The work reported here chiefly accent on magnetostriction and magnetization belongingss of NiFe/FeCo multilayer thin movies. Ni81Fe19 exhibit low coercivity and near zero magnetostriction while Fe50Co50 exhibit high coercivity and high magnetostriction. In simple words this undertaking aims to analyze the alteration in belongingss of FeCo by altering the thickness of NiFe underlayer. A thin movie with low coercivity and high magnetostriction invariable has possible applications in the field of strain detectors. There are three phases involved in this undertaking where in the first phase a figure of multilayer thin movies are fabricated utilizing different techniques like RF spatter, DC spatter and thermic vaporization. Second phase involves word picture of thin movies by MOKE, Villari method, XRD and MFM. Third phase involves of analysis of informations obtained and assorted thin movies are grown. These three phases are successfully completed and expected consequences are obtained which is study is presented here. In simple words this undertaking aims to analyze the alteration in belongingss of FeCo by altering the thickness of NiFe underlayer. Thin movies studied during the undertaking showed some good consequences with low coercivity and high magnetostriction which has applications in the field of strain detectors.
The first histories of Magnetism day of the month back to the ancient Greeks who besides gave magnetic attraction its name. Magnetic compasses have been used from 1000s of old ages ; nevertheless the potency of magnetic stuffs is decently described in twentieth century which laid foundation to modern engineering. The applications of magnetic stuffs are emerging and became indispensable in our day-to-day lives and industries.
Hard and soft magnetic stuffs are important for energy transition, peculiarly for change overing electric energy to mechanical energy, which is of import to run into the challenges of the clime alteration, depletion of fossil fuels and planetary heating. The application of magnetic stuffs in information engineering is increasing quickly. Development in Nanoscience and engineering brought radical advancement in processing and characterizing of stuffs. At the nano graduated table ferromagnetic thin movies are frequently incorporated into multilayered constructions, which have been found to hold magnetic and conveyance belongingss different than realized in bulk magnetic stuffs.
They are chiefly three classs of magnetic stuffs viz. paramagnetic, diamagnetic and ferromagnetic based on orientation of magnetic minutes. Diamagnetic stuffs have no magnetic minutes and no magnetization in zero applied field, nevertheless a little negative minute is induced when field is applied. Paramagnetic stuffs have magnetic minutes indiscriminately oriented throughout the sample giving zero magnetization. When field is applied magnetic minutes align in the way of magnetic field and net magnetization additions with addition in field as the minutes go more ordered. The magnetic minutes become broken when the field is removed. Like paramagnetic stuffs, ferromagnetic stuffs besides have indiscriminately ordered magnetic minutes. When field is applied magnetic minutes align parallel to the field and besides parallel to each other in the way of magnetic field to keep a lowered energy province. The minutes are aligned parallel even when the field is removed.
The work represented here is based on ferromagnetic stuffs Nickel ( Ni ) , Iron ( Fe ) and Cobalt ( Co ) . Properties of ferromagnetic stuffs is determined from hysteresis cringle, hysteresis cringle is obtained when a ferromagnetic stuff is placed in a field which increases from zero to some peak value, decreases to be and opposite value through nothing and so return once more to original peak value. A hysteresis cringle is represented in the Fig 1.1,
Fig 1.1 Hysteresis cringle [ 1 ]
where the impregnation magnetisation ( MS ) represents the maximal value in the way of applied magnetic field that the magnetic dipole minute per unit volume can take. All the magnetic minutes are aligned in the way of field in this province. The remanent magnetisation ( Mr ) represents the staying magnetisation in the sample after the field is reduced to zero from impregnation. The coercivity ( Hc ) is the field required to cut down the magnetisation to zero from impregnation. [ 1 ]
There are two types of magnetic stuffs viz. soft magnetic stuffs and difficult magnetic stuffs. Soft magnetic stuffs are saturated in low Fieldss, but difficult magnetic stuffs need high field to to the full magnetize.
The belongings of being directional dependant is called anisotropy, when internal energy of the system is dependent on the way of the self-generated magnetization so it is called magnetic anisotropy. Two types of magnetic anisotropy is found in ferromagnetic stuffs, magnetocrystalline anisotropy which is related to the crystal symmetricalness of the stuff and magnetostrictive anisotropy which is related to mechanical emphasis.
Interface and volume anisotropy
In multilayers the magnetic anisotropy energy is split in to two constituents viz. volume part and interface part, the relation between these is given as follows
Magnetocrystalline anisotropy in bulk systems in dominated by volume term in bulk systems, nevertheless in multilayer thin movies surface term is becomes more important.
Single ion anisotropy
The interaction between the orbital province of a magnetic ion and the environing crystalline field determines the individual ion anisotropy, which is frequently refered as magnetocrystalline anisotropy. This is present throughout the bed volume of the magnetic bed, and contributes to the volume anisotropy term ; nevertheless add-on or minus of this term depends upon the crystal orientation. It besides contributes to the interface anisotropy ; this is due to the reduced symmetricalness at the interface, nevertheless add-on or minus of this term depends upon the crystal belongingss.
Dipolar interactions determine the form anisotropy of magnetic dipolar anisotropy. This is depending on the form of the sample. This is really of import in thin movies as it produces in plane magnetisation
In a thin movie the dipolar anisotropy energy per unit volume is given by
Where MS is the impregnation magnetization which is unvarying throughout the bed, angle
Ferromagnetic stuff have parts called magnetic spheres, within which the way of magnetisation is mostly unvarying. the sphere size and the orientation of the magnetic minutes in sphere parts are determined by the magnetoelastic, magneto inactive, local anisotropy and sphere wall energy. Spheres are formed in order to cut down the magnetostatic energy, which in bend reduces the internal energy of the system. Exchange energy tends to maintain next magnetic minutes parallel to each other.
Internal energy of the system is besides minimized by the exchange energy and local anisotropy energy by alining the magnetic minutes either parallel to each other or in the local easy axis.
The formation of sphere walls is influenced by the thickness of the movie. in general the spheres walls are aligned as shown in fig, which is called Bloch wall, where the magnetization within the system rotates 180 and can inplane or out of plane.
As the movie thickness lessenings say less than 100nm so different type of sphere walls are formed called Neel wall. As the thickness of the movie decreases domain wall passage occurs from Bloch to neel to diminish magnetostatic energy, nevertheless exchange energy is increased. Complications can originate due to defects such as crystallographic defects, inclusion of drosss with big internal emphasiss which can take to alter in orientation if magnetic minutes.
Pinned sphere walls exists near the interface at which the magnetisation is pinned in a way different from the easy axis of the stuff, this transistion thickness is know as exchange length.
In 1942 Jamess joule found that there is alteration in physical dimensions of a ferromagnetic stuffs when a magnetic field is applied along thee way of magnetization. This phenomenon is known as either J consequence, magnetostriction or magnetoelastic. This occurs due to the internal strain produced in the stuff, which converts magnetic filed into kinetic response. The converse of this consequence I called villari consequence or emphasis induced naisortopy
The energy accumulated due to dipole-dipole interactionsin a ferromagnetic is defined as magnetoelastic energy.
Multilayers and thinfilms
Strain in thin movies and multilayers can be produced by the growing conditions, such as lattice mismatch between beds or thermic emphasis caused by differences in thermic enlargement coefficients of adjacen
Undertaking route map
This work involves three phases where in the first phase a figure of thin movies are fabricated utilizing different fiction techniques like releasing factor spatter, District of Columbia spatter and thermic vaporization. In the 2nd phase the thin movies grown are characterised by MOKE gaussmeter, XRD and MFM. In the concluding phase informations obtained from the word picture phase is analysed and more movies are grown harmonizing the consequences obtained. This procedure is shown in the signifier of block diagram in the below diagram.
Fabrication of Ni81Fe19 and Fe50Co50 multilayer thin movies utilizing different techniques
Transverse MOKE gaussmeter is used to look into belongingss of thin movies
Magnetostriction invariable ( ?s ) of thin movies is measured by utilizing villari theoretical account.
By utilizing XRD and MFM
Measuring the consequences from the above stairss
Adding NiFe beds or changing the thickness of the bed
Consequences and treatment
Thin movies with low coercivitry and high magnetostriction have possible applications in the field of strain detectors. Which is mems applications, one of such application is discussed below.
see are based on polycrystalline Fe-Co. The metal
series has been studied in bulk signifier for many old ages [ 20 ] with
a bcc solid solution bing across the composing scope
of 0 % -60 % Co. The impregnation magnetostriction invariable
extremums at the broken equi-atomic composing, with
a value of 150 ppm. Taking published informations for the impregnation
magnetostriction invariables of Fe Co [ 20 ] , [ 21 ] , an isotropous polycrystal should demo a net magnetostriction invariable of about
80 ppm. We have demonstrated [ 22 ] that this degree
of magnetostriction can be achieved in polycrystalline 300 nanometer
thick movies on glass substrates, but at the disbursal of coercivities
greater than 500 A/m even after tempering. The anisotropy field
was 3800 A/m. Work continues to research paths
to bring forth extremely textured FeCo movies, utilizing appropriate seed beds, in order to accomplish higher net magnetostriction invariables
for the movies.
Write about shoms project..a brief treatment… one hope I had an paper
Properties of NiFe
NiFe is known as Permalloy. Permalloy exhibit high magnetic permeableness, low coercivity near zero magnetostriction and important anisotropic magentoresistance. There are three composings of metals. Of these 78 % per centum Ni and 22 % Fe has near zero magnetostriction and magnetocrystalline anisotropy and besides high initial permeableness. Nickel 65 % exhibits a strong response to field tempering while keeping k1~0, 50 % Ni with staying Fe has higher flux denseness every bit good as their reactivity. The crystal construction of Permalloy is by and large face centered three-dimensional construction. For alloys with 30 % Ni the construction is Body centered three-dimensional construction. Permalloys with Curie temperature more than 400o respond really good to magnetic field. There are four anisotropies that can happen in NiFe, they are magnetocrystalline anisotropy, magnetoelastic anisotropy, thermomagnetic anisotropy and faux pas induced anisotropy. All these can be avoided by tempering and by seeking k1 and ?=0. [ 1 ]
Properties of FeCo
FeCo is a soft magnetic stuff, it is known as permendur which means 50 % of Cobalt and 50 % of Iron. These exhibit really high impregnation initiation, low magnetic anisotropy, big magnetic permeableness and high Curie temperature. An equiatomic FeCo shows order-disorder transmutations. These transmutations occur at 730o. Properties of ordered and broken FeCo are different. FeCo at above 950o shows face centered three-dimensional construction ; below 850o it shows organic structure centered three-dimensional construction. Below 730o it forms telling, which exhibits high coercivity. [ 9 ]
Permalloys and permendurs are used as constituents of the sense bed spin-valve read caputs. Coercivity and magnetic anisotropy of NiFe lessenings with lessening in thickness regardless of the movie construction when it is sandwiched with Ta. In FeCo movies they exhibit an addition in coercivity and magnetic anisotropy with lessening in thickness below 100 Ao, here the magnetic anisotropy appears to be magnetoelastic in nature [ 2 ] . Soft magnetic belongingss of FeCo bed are best at the thickness of ~100nm. As FeCo has big magnetostriction it is hard to accomplish soft magnetic belongingss. When these movies are sandwiched with NiFe, they show soft magnetic belongingss at 2.4T of impregnation magnetization. [ 3 ] FeCo movies by and large shows high coercivity values over 50 Oe with no distant uniaxial anisotropy. Coercivity can be reduced by proper nitridation or deposition on assorted under-layers. An appropriate under-layer can better the soft magnetic softness of FeCo movies. Increase in movie thickness increases the coercivity due to increase of grain size. [ 4 ] FeCo metal shows big additive magnetostriction invariable. The coercivity of FeCo metal along the difficult axis lessening as the lessening in Ar force per unit area during the sputtering deposition, and besides shows that it exhibits low coercivity at a thickness of 50-100nm [ 5 ] The high coercivity of FeCo bed can be decreased from 140 to 12 Oe when FeCo is grown on CoO, it is due to the lessening in grain size from 20-35 to 5-15nm. [ 6 ]
These FeCon and feco metal shows a big impregnation magnetostriction invariable in the scope of ( 40-65 ) ppm and a comparatively high anisotropy changeless k1 of I?I?10kj/m-3, which make it hard to accomplish good magnetic softness in the feco and fecon metals
A coercivity of 960 A/m s12 Oed was
achieved in a 30-nm-thick FeCo50 at. % metal movie seeded
with a thin CoO layer.3 The soft magnetic attraction in the CoOseeded
FeCo movie was believed to be due to the all right grain
size induced by the CoO seedlayer.3 A coercivity of
400 A/m s5 Oed was achieved in the 100-nm-thick FeCoN
swith,30 at. % Cod films.4 A really thin,2.5-nm-thick Permalloy
metal movie was used as a seedlayer for the FeCoN movie
with a thickness of 100 nanometers, which resulted in a low coercivity
of less than 80 A/m s1 Oed.4,5 Similar magnetic softness
was achieved in 50-nm-thick FeCo35 at. % metal movies
seeded with a thin bed of NiFe, Cu, and Ru, which showed
a low coercivity of 80-240 A/m s1-3 Oed in the difficult
axis ; 6,7
The mean grain sizes of the
NiFe- , Cu- , and Ru-seeded 30-nm-thick FeCo35 at. % movies
were found to be in the scope of 10 nanometers, which was in contrast
to the mean grain size of,50 nanometer in the Ta-seeded
FeCo movie that did non demo good soft magnetic belongingss.
The magnetic softness in the FeCo movies on NiFe, Cu, and
Ru was attributed to the all right grain sizes induced by the seedlayers.6,7 A low coercivity of 720 A/m s9 Oed was reported
in a single-layer FeCo movie, which was besides attributed
to a little mean grain size of 7.2 nm.11
The mean grain size normally increases with the movie
thickness, which frequently causes deteriorated soft magnetic
belongingss, as shown in the FeCo50 at. % films.2 Stripe sphere
signifiers when the movie thickness reaches a certain bound in
a soft magnetic movie which degrades the magnetic
softness.12,13 Most of the published informations on soft magnetic
FeCo and FeCoN movies showed a thickness of
Ref codification 1
These belongingss include low coercivity, low
crystalline anisotropy, big magnetisation, little magnetostricti
on, and comparatively big magnetoresistive coefficient.
The thickness of Permalloy movie, in most applications,
varies from several nanometres to several microns.
However, the shear emphasis at the substrate and movie interface
additions as the movie thickness increases.4
5 When a critical
thickness is reached, the shear emphasis is greater than the output
emphasis at the interface doing the movie to lose adhesion. Movies
holding compressive emphasis buckle and movies holding tensile
emphasis psychiatrist or cleft, hence, the in-plane emphasis of the
movie has to be controlled really carefully to guarantee the movie ‘s
unity and dependability.
The fluctuation of emphasis with movie thickness has been observed
in man.y metallic movies, and can be attributed to the
morphology difference at different movie thickness. Several
different mechanisms for the beginning of the thin movie ‘s intrinsic
emphasis have been reported.2
! ,22 These mechanisms include
lattice enlargement, surface tenseness, grain size coalescency, consequence
of the tempering of the grain boundary, defects, and dross
incorporation. During the movie growing, one or several
of these mechanisms can go dominant at a given thickness.
Ref codification 2
A little lattice distortion in FeCo alloy movies outputs significantly
big magnetostrictive energy of grains because of big
additive magnetostriction invariables, ensuing in degraded magnetic
softness [ 3 ] . Therefore, the visual aspect of soft magnetic
belongingss in the FeCo/NiFe ( Cr ) movie is likely related to the
decrease of lattice distortion besides the decrease of grain
size [ 3 ] , [ 4 ] . Furthermore, it is likely that a high grade of preferable
grain orientation, which is frequently achieved by the usage of seed
beds, plays an of import function to deduce soft magnetic belongingss
in FeCo movies [ 5 ] , which may take to the visual aspect of softness
in FeCo/NiFe ( Cr ) movies.
It is likely that less lattice distortion, besides comparatively
little grain size and extremely preferable grain orientation, is a key
to deduce soft magnetic belongingss in the FeCo metal movies, and
the hetero-epitaxial growing of FeCo ( 110 ) plane on NiFe ( 111 )
plane consequences in a high stableness and duplicability of the soft
magnetic belongingss of FeCo movies.
Ref codification 3
The humdrum alteration of cubic decimeter with diminishing tmag can
be attributed to the laterality of interface magnetostriction
at smaller movie thicknesses.3 While Nee?l ‘s two-component
description3 of magnetostriction, ls5lb1li / ( tmag2t0 ) , is
valid over a comparatively big thickness scope for NiFe movies, it
is merely effectual over a limited thickness scope for CoFe
movies. As shown in Fig. 4, the one-dimensionality of ls V 1/ ( tmag
2t0 ) curve exists over the thickness scope of 35 & A ; Aring ; , tNiFe
& A ; lt ; 200 & A ; Aring ; for NiFe movies and of 80 & A ; Aring ; , tCoFe & A ; lt ; 200 & A ; Aring ; for CoFe
movies. The majority constituents, pound, and the interface constituent,
Li, have been estimated by suiting the information to the twocomponent
look. The consequences are listed in Table I. pound
scopes from 21.7831026 to 21.9931026 for NiFe movies
and from 23.5831026 to 25.56331026 for CoFe movies.
The interfacial part, Li, of CoFe movies is about 10
times larger than that of NiFe movies. Although there exist
important differences in the thickness dependance of cubic decimeter
among the three series of NiFe or CoFe movies, the values of
cubic decimeters are typically in the 1026 scope.
Ref codification 4
It was found
that the Permalloy underlayer, instead than the cap bed, is
more of import in accomplishing the low coercive Fieldss in Fe-
Co-N films.3 The magnetic softness of polycrystalline thin movies is
closely related to the structural and compositional features
in the thin movies, such as grain size,5 crystallographic
texture,6 and strain and emphasis state.7 These features
can besides impact the other belongingss such as anisotropy and
magnetorestiction, which are closely correlated with the
Another possible cause for the magnetic softness may be
related to the magnetoelastic anisotropy that is determined
by the emphasis province and impregnation magnetostriction in the movie.
The impregnation magnetostriction invariables of the Fe-Co-N
movies with different Permalloy underlayer thicknesses bead
somewhat with the addition of Permalloy underlayer thickness,
as shown in Fig. 4.
Ref codification 5
metallic thin-film multilayered constructions. This consequences both
from magnetotransport effects that the stuffs show @ e.g. ,
elephantine magnetoresistance ~GMR! ~Ref. 1! # , and from their
widespread applications in the informations storage industry
This yields an interface breadth ~defined as
10 % -90 % of the nominal bed composings! of ; 1.2 nanometer.
By comparing, the interface produced when CoFe is grown
on NiFe, shown on the left side of the Fig. 2 profile, is found
to be more diffuse, with a mensural breadth of ; 1.8 nanometer. Averaging
the measurings over profiles taken from three different
countries across the interfaces outputs breadths of 1.1
60.2 nanometer for NiFe grown on CoFe and 1.760.2 nanometer for CoFe
grown on NiFe.
Ref codification 6
Previous work has studied the consequence of underlayers
[ 3,4 ] , the substrate stuff [ 5 ] and the rate of deposition
[ 6 ] on the magnetic belongingss of Fe1-xCox movies ( where ten
scopes from 35 to 65 ) . Jung et al studied 50 nanometers Fe65Co35
movies grown on glass substrates and on thin Cu underlayers
[ 4 ] . They found that the Cu underlayer induced a uniaxial
anisotropy into the movies compared to the isotropic movies
grown merely on glass. The Cu underlayer besides reduced the
coercive field and the emphasis in the movies. The
magnetostriction remained around ~ 50 ppm, although the
construction changed from & A ; lt ; 200 & A ; gt ; texture with no Cu bed to
& A ; lt ; 110 & A ; gt ; texture with the Cu underlayer. Jung et Al besides
studied other metallic underlayers [ 3 ] , and found that
NiFe, Ru and Ta/NiFe beds besides induced uniaxial
anisotropy in the FeCo movies, while cut downing the movie
emphasis. They determined this was due to the underlayer
altering the texture of the movie from & A ; lt ; 200 & A ; gt ; on glass to
& A ; lt ; 110 & A ; gt ; .
with Cu radiation [ 12 ] . It is observed that for all the movies
the & A ; lt ; 110 & A ; gt ; extremum has its centroid above 45o. This may be
due to emphasiss in the movies or the sample tallness
supplanting. Assuming that the displacement in the extremum was due
to emphasiss in the movies, the lattice invariables were besides
determined ( Fig. 3b ) . For all the movies the lattice invariables
were smaller than the majority value. Taking a Young ‘s
modulus for a 2?m midst FeCo movie on Si as Y = 165 GPa
[ 13 ] , and the mean strain given by the alteration in lattice
parametric quantity depicted in Fig. 3b, gives a compressive emphasis
of ? = 1.4GPa on the movie. This is non an unreasonable
value as pickings,
2 net K? = ? ? ( 4 )
with ?net = 30 ppm, yields a stress anisotropy invariable of
K? ~ 6.3×103 J.m-3. This in bend outputs an anisotropy field
= ( 5 )
of 53 kAm-1 utilizing a impregnation initiation ( ?0Ms ) of 2.4 T,
which is of the order of the measured values ( 60 nm DC
non-rotated movie ) . The RF non-rotated and 600K DC
rotated movies had lattice invariables closest to the majority value
proposing a lower movie emphasis than in other movies. It is
these movies that most closely follow equation ( 1 ) . This may
imply that the surface/interface magnetostriction does non
dominate in movies holding high emphasis. Further probe
is required, get downing with a simple post-deposition anneal
of these movies to cut down the residuary emphasis.
Ref codification 7
FeCo movies typically
demo in-plane about isotropous square hysteresis cringles with
coercivity Hc.80 Oe @ Fig. 1~a! # .2-4 The impregnation magnetostriction
is besides really large1 with values of the changeless cubic decimeter
from 45- 6531026 which in polycrystalline movies if emphasiss
are big, can ensue in big inhomogeneous local magnetostrictive
anisotropies and potentially high Hc. However, Platt
et al.3 reported that a important decrease in Hc from 140 to
12 Oe was observed when Fe50Co50 was grown on CoO.
Based on microstructural and other informations, they concluded that
the cause was a decrease in grain size from 20-35 to 5-15
nanometer. Wang et al.,5 besides reported that similar consequences could be
obtained if ( Fe70Co30 ) N movies were grown on NiFe. Later,
they6 proposed that increased exchange yoke between the
( Fe70Co30 ) N grains mediated by the NiFe underlayer caused
the coercivity decrease
We demonstrate that the primary consequence of the Cu, NiFe,
and Ru underlayers is to cut down grain size in FeCo, which
causes a decrease in Hc quantitatively consistent with rippling
Ref codification 8
Thin movies are adult utilizing different techniques like sputtering and vaporization
Silicon substrate is used throughout the undertaking. Substrate has significant effects in the alteration in belongingss of the movie. Exchange matching Acts of the Apostless at the interface
& A ; lt ; 100 & A ; gt ;
Nordiko NM2000 sputtering system is used to sputter sedimentation the NiFe and FeCo thin movies by wireless frequence ( RF ) magnetron sputtering. This procedure includes formation of plasma by pelting the mark with inert gas ions, which causes expulsion of atoms from the mark stuff. The atoms that are ejected from the mark are made to sputter on the substrate, which in bend signifiers the thin movie. Spatter of atoms on to the substrate depends on the sputtering parametric quantities i.e. , force per unit area and power. Sputter-up manner is used i.e. , substrate is placed above the mark, which are separated by a distance of 6cm. Three mark electrodes can be used at a clip to sputter multi-layered movies in Nordiko NM2000. Growth rate of thin movies is high as magnetron beginning is used, and chiefly depends on the sputtering parametric quantities viz. sputtering power and force per unit area. Growth rate can be increased by increasing the sputtering power, which in bend increases the temperature. Growth rate can besides be increased by increasing the force per unit area at low force per unit areas. [ 1 ]
The belongingss of the ensuing thin movies are sensitive to sputtering power, temperature and force per unit area. Two types of substrates are used viz. silicon-based and glass-based substrates, which are cleaned by rinsing in propanone and isopropyl alcohol. Clean-room baseball mitts and non-magnetic pincers are used to manage the substrates. The conventional diagram of sputtering system is shown in fig [ 1 ] .
The composing of Fe ( Fe ) in NiFe mark is 19 % and 50 % in FeCo mark. In order to look into the belongingss of NiFe and FeCo thin movies a scope of movies are grown with different thicknesses. This undertaking chiefly aims at the belongingss of NiFe and FeCo multilayered thin movies, but during the class of developing a broad scope of monolayer movies are grown. Five thin movies are grown of which four are monolayers and one multilayer, which are grown on Si substrate. These are grown based on the antecedently calibrated values of NiFe and FeCo, as shown in Table 1.
Table 1 Calibrated values of NiFe and FeCo thin movies
Ar Pressure ( mTorr )
Base force per unit area ( Torr )
Forward power ( W )
Time ( min )
Thickness ( nanometer )
6.5 X 10-6
6.5 X 10-6
Fig [ 1 ] Schematic representation of Nordiko NM 2000 [ 1 ]
The tabular array below shows the samples and the turning conditions at which the thin movies are grown. Thickness of the sample depends on the spatter clip and sputtering rate. Table 2: Growth parametric quantities of the thin movies
Ar Pressure mTorr
Base Pressure ( Torr )
Forward power ( W )
Rearward power ( W )
Time ( min )
Thickness ( nanometer )
6.5 x 10-6
75 ± 4
6.5 x 10-6
6.5 x 10-6
6.5 x 10-6
6.5 x 10-6
20 ± 2
Base force per unit area 8e-8
Time 4 min
Growth force per unit area 7e-3 mbarr
Temperature room temperature
All of the constructions studied here were patterned from thin movies deposited utilizing a Wordentec thermic evaporator, shown schematically in fig. 3.4. The deposition stuff was placed in an aluminum oxide covered tungsten-wound crucible and the evaporator was evacuated to a basal force per unit area of ~ 3-10-7 mbar. An electric current was passed through the crucible to heat the stuff and initiate vaporization. Evaporated stuff migrated towards the sample substrates, fixed to an indexed substrate holder utilizing a 4:21 PMMA/anisole mixture, and an Edwards FTM5 movie thickness rate proctor. A mask in forepart of the substrate holder enabled up to five different depositions and besides allowed the deposition rate to be monitored without lodging stuff onto a substrate. The rate proctor measured the deposition rate and the deposited thickness with a declaration of 1 & A ; Aring ; /s and 1 & A ; Aring ; , severally. Once the coveted thickness had been deposited, a shutter was used to barricade evaporated stuff making the substrates. After deposition, the sample thickness was confirmed utilizing an atomic force microscope
Word picture techniques
MOKE ( Magneto Optic Kerr Effect ) gaussmeter is used to analyze the belongingss of thin movies that were grown. Optical anisotropy is observed in magnetic stuffs when external magnetic field is applied, this is due to the magnetization of surface spheres. Magneto ocular effects will originate due to the presence of optical anisotropy, which is besides known as magneto-optic kerr consequence. This consequence is used to obtain hysteresis cringles of the thin movies.
He-Ne optical maser is used with wavelength ( ?=633nm ) which is made to incident on the sample at an angle of 450. Before the visible radiation is made to incident on the sample, visible radiation is p-polarized by a Glan Taylor polariser and passed through a lens of focal length 30cm. The reflected visible radiation from the thin movie is made to go through through analyzer onto a photo- sensor. The strength of the visible radiation was measured by the photo-detector and by utilizing a computing machine based plan a hysteresis cringle is obtained. The sample holder can be rotated freely in the plane of the magnetic field through 360o. [ 1 ]
For each thin movie informations is obtained by revolving the sample holder from 0o to 180o at an interval of 30o. For all the graphs 256 information points are taken with a form factor of 0.4 and analyser angle 30o grades. To acquire the accurate informations three norms are taken. As the experiment is conducted in unfastened environment, noise is included in the information. Hence impetus and symmetricalness of the cringle should be corrected ; this can be done by normalizing the information. This includes a series of stairss to be performed utilizing Microsoft excel plan. The information obtained is utilized to find coercivity, remanence and impregnation point of each thin movie.
By externally striving the thin movie we can find the magnetostriction of the movie. These movies are strained under flexing radii of 300mm, 400mm and 500mm, and are investigated by utilizing MOKE. Eight mean readings are taken with 256 informations points and form factor 0.4. Data is so normalized in order to cut down the noise. Magnetostriction can be calculated from the expression [ 2 ]
Hk is the anisotropy field, ? is thickness of the substrate, Y is immature ‘s modulus of the substrate, R is the crook radius, V is Poisson ratio of the substrate.
Fig 2, MOKE magnetometer [ 2 ]
The magnetostriction invariable is determined by Villari method. It involves striving of movies i.e. , flexing the movies over five known radii and mensurating the magnetization cringle. It is given by
Hk is the anisotropy field, ? is thickness, Y is immature ‘s modulus, R is the crook radius, V is Poisson ratio. [ 12 ]
We use XRD ( X-Ray Diffraction ) to find the grain size and alteration in lattice invariable of the thin movie. It characterises the texture of the movies. The mean grain size in the movies is determined utilizing Scherrer equation [ 12 ] .
Mhos D5000 xray diffractrometer is used to find the grain size and lattice invariable in thin movies. These are observed in the scope of 30-80 grades with an increase of 0.2 per minute.
A magnetic force microscope ( MFM ) is basically the same as an atomic force
microscope ( AFM ) . However, the scanning investigation is coated with a bed of magnetic
stuff, which may be magnetically difficult ( e.g. , CoCr ) or magnetically soft ( formless
ferromagnetic metal ; e.g. , FeBSiC ) ; a tip is shown in Figure 4.24. It is usual to take a line
scan in contact manner to give the topographic information, and so rescan the line at a
fixed winging tallness of a few 10s of nanometers to obtain the magnetic contrast. In
contact manner new wave derWaals forces, which have a much shorter scope than the magnetic
forces, dominate and merely topography is seen. At the winging tallness, the longer-range
magnetic interactions between the tip dipole minute and the isolated field from the sample
are detected ( Figure 4.25 ) .
An oscillating cantilever ( typically 70 kilohertz ) would typically be used for high sensitiveness.
The tip is sensitive to the force gradient @ Fz/ @ z, which modifies the effectual
cantilever spring changeless keff: this produces a alteration in angular frequence
! 0 ?
keff _ @ Fz= @ omega
& A ; deg ; 4:36 & A ; THORN ;
where me is the mass of the cantilever. If, as is usual, @ Fz/ @ z _ keff so we can compose:
0 ? ! 0 1 _ @ Fz= @ omega
so _ ! ? !
0 _ ! 0 _ _ ! 0
: & A ; deg ; 4:37 & A ; THORN ;
For an attractive force there is a lessening in resonance frequence, and frailty versa ; this
alteration is used to bring forth the contrast. As an illustration, Figure 4.26 shows informations from a