Cocu au maximum
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Cocu au maximum
October 2009 Technical Physics Letters 35(10):903-905
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A new method for the formation of functional elements of spin-valve structures is proposed, which is based on the sequential
condensation of nanodimensional Co, Cu, Au, and Cr layers with certain heat treatments in the course of condensation. The
magnetooptical and magnetoresistive properties of structures obtained using the proposed method have been studied. Relationships
between these properties and the structure and phase state of the spin-valve sandwiches and their components are established.
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ISSN 10637850, T echnical Physics Lette rs, 2009, V ol. 35, No. 10, pp. 903–905. © Pleiades Publishing, Ltd., 2009.
Original Russian T ext © I.V. Ches hko, S.I. Protsenko, L.V. Odnodvorets, P . Shif alovich, 2009, published in Pis’ma v Zhurnal T ek hnichesko
Fiziki, 2009, V ol. 35, No. 19, pp. 53–
Materials characterized by spindependent elec
tron scattering, which are based on Co–Cu(Au) mul
tila yers, poly crystalline alloy films, and spinvalv e
structures, are widely used in modern technology of
microelectronic devices and sensors [1]. In particular ,
a v ery promising application of these materials is
related to the creation of largecapacitance energy
stores. A relativ ely simple manufacturing technology
and broad spectrum of possible applications explain
the extensiv e experimental and theoretical inv estiga
tion of physical processes taking place in these thin
film systems. How ev er , methods used for the manu
facture of spinv alv e structures (see, e.g., [2, 3]) w ere
based in many cases only on the results of inv estiga
tions of their magnetotransport properties, while the
issues pertaining to features of the structure, phase
state, and diffusion processes in relation to the magne
toresistiv e characteristics w ere giv en much less atten
T aking into account the results of inv estigations
of the structure and phase state of bila yer film sys
tems based on the materials with spindependent
electron scattering—Cu(Au, Ag) and Co [4]—w e
selected an optimum configuration of the func
tional element of spinv alv e structures in the form
o f a multila yer thinfilm system
Au(3)/Co(3)/Au(Cu)(6)/Co(20)/Au(40)/Cr(3)/Sub
(where Sub is the substrate and v alues in parentheses
indicate the corresponding la yer thickness in nanome
The multila yer thinfilm structures w ere manufac
tured by the thermal ev aporation of components
under ultrahighv acuum conditions (residual pres
P a) on Si(001) single crystal substrates. The
w orking magnetic la yers of Co, which w ere separated
by 6nmthick nonmagnetic la yers of Cu or Au, had
different thicknesses. The thickness of the upper
(“soft”) la yer w as about 15% of that of the low er
(“hard”) la yer (3 and 20 nm, respectiv ely). This com
bination ensured operation of the entire spinv alv e
structure in a magnetic field in accordance with the
scheme depicted in Fig. 1. According to this, the upper
Co la yer is more sensitiv e to changes in the magnetic
field and, hence, the magnetization rev ersal in its
domain structure begins at smaller v alues of the field
than that in the low er lay er (which exhibits a greater
Magnetooptical and Magnetoresistive Properties
of Co/Cu(Au)Based SpinValve Structures
Sumy State University , 40007 Sumy , Ukraine
Institute of Physics, Slovak Academy of Sciences, 84511 Bratislava, Slovakia
*email: protsenko@aph.sumdu.edu.ua
—A new method for the formation of functional elem ents of spinv alv e structures is proposed, which
is based on the sequential condensation of nanodimensional Co, Cu, Au, and Cr la yers with certain heat
treatments in the course of condensation. The magnet ooptical and magnetoresistiv e properties of structures
obtained using the proposed method hav e been studied. Relationships between these properties and the struc
ture and phase state of the spinvalv e sand wiches and their components are established.
P A CS numbers: 75.47.De, 73.21.Ac, 61.16.Bg
Schematic diagrams illustrating the structure
A u( 3 ) /Co(3)/Au(Cu)(6)/Co(20)/Au(40)/Cr(3)/Sub spin
v al v e in a magnetic field. The arrows indicate the directions
of magnetization in the uppe r and low er magnetic la yers.
TECHNICAL PHY SICS LETTERS V ol. 35 No. 10 2009
resistance to the magnetization rev ersal). The giant
magnetoresistance (GMR) is just manifested in the
netic inductions corresponding to the onset of magne
tization rev ersal in the lowe r and upper la yers, respec
tiv ely . The auxiliary thin (3 nm thick) Cr la yer ensures
a high adhesion to the substrate, while not mixing with
the 40nmthick Au la yer that pla ys the role of the
low er electric contact. The upper 3nmthick Au lay er
also pla ys the roles of the electric contact and a protec
tiv e film for the entire structure. The spacer (inter
la yer) material w as chosen on the basis of data accord
ing to which systems with Cu/Co and/or Au/Co bila y
Thus, according to the proposed scheme, a differ
ence betw een the coercivities of the lower (“hard”)
and upper (“soft”) Co la yers is ensured by the differ
ence in their thicknesses. The difference betw een the
m a g n et ic ch ar ac te ri st ic s o f l a y er s c an be en ha nc ed by
means of an additional heat treatment. W e propose to
form the low er and upper Co lay ers at different tem
peratures of the substrate. The low er (thicker) lay er
was deposited at a substrate temperature of
while the upper (thinner) la yer w as deposited at room
temperature. This idea is based on the results of inv es
tigation of the magnetooptical Kerr effect (MOKE) in
singlela yer Co films obtained at v arious substrate
temperatures. In films formed at the high tempera
ture, the coercivity w as 5–6 times greater than that in
the films obtained at room temperature.
W e hav e thoroughly studied the magnetic charac
teristics of nonheattreated singlela yer Co films and
those annealed at v arious temperatures, which exhib
ited anisotropic coercivity . The maximum anisotropy
w as observ ed for the initial low annealing tempera
= 350–500 K). This can be explained by fea
tures of a change in the crystalline structure of these
singlela yer Co films. At the initial stage, Co films
annealed at low temperatures exhibit selfhealing of
structural defects, which leads to impro v ement of the
domain structure that is manifested by increased mag
netic anisotropy of a sample. Significant changes in
MOKE in va rious systems: (a) Au(15)/Co(
)/Sub with different thicknesses of Co la yers, measured upon the annealing at
= 700 K; (b) Au(5)/Co(3)/Cu(6)/Co(20)/Au(40)/ Cr(3)/Sub annealed at v arious temperatures;
(c) Au(3)/Co(3)/Au(6)/Co(20)/Au(40)/Cr(3)/Sub an nealed at various temperatures; (d) same for
Au(5)/Co(3)/Cu(6)/Co(20)/Au(40)/Cr(3)/Sub with the low er Co lay er deposited at
TECHNICAL PHY SICS LETTERS V ol. 35 No. 10 2009
MAGNETOOPTICAL AND MAGNETORESISTIV E PROPERTIES 905
the film structure take place upon the annealing at
600 K that leads to a transition to the fcc phase,
which is accompanied by a sharp increase in the av er
age size of grains, a growth in the coercivity , and the
loss of pronounced magnetic anisotropy .
On the passage to Cu/Co and Au/Co bila yer sys
tems, the form of the MOKE signal exhibits a change
that confirms conclusions [3, 4] concerning the for
mation of Cu–Co and Au–Co solid solutions in these
bila yer structures. Indeed, in Au/Co systems with v ar
ious Co concentrations, the heat treatment at
700 K alw a ys led to a normal character of the MOKE
curv es with a hysteresis loop, which correspo n d e d t o
the formation of Co grains in the Au–Co solid
solution matrix. In the Cu/Co system, the hyster
esis loop exhibited no significant changes upon the
explained by the fact that a solid solution w as
already formed during the condensation. Figure 2a
shows a co mparison of the MOKE curv es of
40 nm, which corresponds to v arious contents of
In the spinv alv e structures with Cu and Au spacers
(Figs. 2b and 2c, respectiv ely), the MOKE is deter
mined by the low er (“hard”) Co lay er . The annealing
of all systems with Cu la yers did not lead to significant
changes, since the solid solution w as already formed
during the condensation. Considerable changes in the
MOKE curv es are observed for the spinv alv e struc
tures with Au spacers upon the annealing at
700 K, which is apparently related to the formation of
an Au–Co solid solution in the entire v olume. This is
confirmed by the MOKE curv e of the
Au(5)/Co(3)/Cu(6)/Co(20)/Au(40)/Cr(3)/Sub
(with the low er Co film deposited at
Fig. 2d, where the hysteresis loop exhibits a stepped
shape. This is evidence for a fast response of the func
tional element to the magnetic field v ariations, which
makes possible the operatio n of this element in the
Figure 3a shows plots of the magnetoresistance
magnetic induction for functional elements based on
the Au(5)/Co(3)/Cu(6)/Co(20)/Au(40)/Cr(3)/Sub
structures annealed at v arious temperatures. The
ascertain that GMR is present in this system. Figure
c u r v e s o f s p u n v a l v e s t r u c t u r e s
with v arious thicknesses of Cu spacers. The maximum
in a narrow interv al of magnetic fields is observ ed
for the structure with a spacer thickness of 6 nm. This
can be related to an oscillating dependence of the
on the nonmagnetic spacer thickness.
E. Maiko v a for fruitful discussion of results.
This study w as performed within the framew ork of
the project of scientifictechnical cooperation
betw een the Sumy State Univ ersity (Sumy , Ukraine)
and the Institute of Physics of the Slo v ak Academy of
2. B. Dieny , V . S. Speriosu, B. A. Gurney , et al., J. Magn.
3. A. I. Moroso v and I. A. Moroso v , Fiz. T v erd. T ela
4. S. I. Protsenko, I. V . Cheshko, D. V . V elikodnyi, et al.,
5. M. P annetierLecoeur , C. Fermon, A. de Vismes, et al.,
Magnetoresistance of th e functional elements of
spinvalv e structures: (a) Au(5)/Co(3)/Cu(6)/Co(20)/
Au(40)/Cr(3)/Sub with the low er Co la yer deposited at
... But the result is a reduction in the effective performance of such structures. Authors [8] offer a technique for additional thermal treatment of individual layers of these metals in the process of receiving spin-valves although this only achieves a temporary beneficial effect. An alternative may be to use a layer material from other metals, such as a Gd or Dy layer as shown in the works [9,10]. ...
Представлені результати дослідження кристалічної структури, фазового складу та дифузійних процесів у плівкових системах на основі Co та Ru в діапазоні товщин 5÷60 нм до і після відпалювання до температури 600 К. Було показано, що плівкові системи Co / Ru / П та Co / Ru / Со / П складаються з фази ГЩП-Co та ГЩП-Ru. Плівкові системи до складу яких входять шари Ru до і після відпалювання мають нанодисперсну кристалічну структур. Середній розмір кристалітів зразків до відпалювання не перевищує 3÷5 нм, після відпалювання максимальний середній розмір становив 16 нм для зразків з товщиною шарів 60 нм Результати дослідження дифузійних процесів двошарових плівкових систем Co / Ru / П в різних діапазонах товщин показали, що до і після відпалювання зберігається відносна індивідуальність окремих шарів оскільки розраховані значення ефективних коефіцієнтів термічної дифузії для відносно тонких та відносно товстих плівок лежать в межах від 0.1 до 1.1 · 10 - 19 м² / с.
The generalized literary data and results of own experimental investigations of structural and phase state, stability of interfaces and electrophysical properties (thermal coefficient of resistance (TCR) and strain-gauge factor (SGF)) for two-layer film systems, Cu/(Co, Ag or Au), Cu/(Cr or Fe) and Fe/Cr, are presented. The choice of these systems is caused by stabilization of various structural and phase states in them such as granular solid solutions (systems based on Cu and Co, Ag or Au), solid solutions (Fe/Cr), two-layer systems with conservation of individuality of separate layers (biplate) (Cu/Cr and Cu/Fe systems (below 700 K)). Experimental results for TCR and SGF agree well or satisfactory with relationships for TCR and SGF of the biplate, film alloy or two-layer system with an intermediate layer of solid solution near the interface. It can serve as an additional argument in favour of conclusions concerning structural and phase state of two-layer system. © 2018 G.V. Kurdyumov Institute for Metal Physics of N.A.S. of Ukraine. All rights reserved.
We demonstrated in a variety of systems that the in-plane resistivity of sandwiches of soft ferromagnetic layers separated by nonmagnetic metallic layers depends on the relative angle between their magnetizations. We observe this phenomenon, which we term the spin-valve effect, in sandwiches where we are able to control the relative angle between the magnetizations of two ferromagnetic layers either by constraining one layer through exchange anisotropy or by fabricating layers with different coercivities. In the first case, for example Si/50Å Ta/60Å NiFe/25Å Cu/40Å NiFe/50Å FeMn/50Å Ta we have seen relative changes in resistance of more than 4% at room temperature in a range of in-plane field of 0 to 15 Oe. In a system where the layers have different coercivities, Si/8 × (30Å Fe/60Å Ag/30Å Co/60Å Ag), we observed a relative change of 1.6% at room temperature for fields between 0 and 50 Oe. Since the ferromagnetic layers are essentially decoupled and have high squareness, one can rule out any mechanism requiring scattering by domain walls. The usual anisotropic magnetoresistance in these structures is much smaller than the spin-valve effect. In contrast to noble metals, when using Ta, Al, Cr or Pd spacers of similar thickness (20 to 150Å) between layers of permalloy, only the anisotropic magnetoresistance is observed. We believe the spin-valve effect to be related to spin-dependent scattering at the interface and within the ferromagnetic layers, in balance with spin-dependent relaxation within the layers. We also report the observation of a weak exchange-like coupling between the ferromagnetic layers.
Magnetoresistive materials are widely used for read-heads and are very good candidates for sensors due to their sensitivity. A large number of applications, at present covered by Hall sensors, can be targeted but they require having stable, reproducible, hysteresis-free and high signal-to-noise devices. This can be addressed by optimizing the material aspect (stack composition, magnetization direction) and the design. External biasing applied to giant magnetoresistance (GMR) sensors by integrated permanent magnets can be used to tailor the response and stabilize the sensor against random fields. In this paper, we present the work we have performed to tailor GMR samples to fulfill the requirements of two specific applications. In the first case we have developed very stable and reproducible current sensors with the aim of permanent magnet biasing. In the second case we show results on a single-chip 2D compass, where the Earth's field measurement is obtained by a local magnetization reversal of the hard layer. The sensitivity of this compass is 3° for a current consumption of 200 μA.
The thickness-roughness phase diagram of a ferromagnet-antiferromagnet-ferromagnet spinvalve system is studied in the case
where the roughness of the interfaces between the layers causes frustration of the exchange interaction between them. It is
shown that the inclusion of easy-axis single-ion anisotropy makes the phase diagram significantly more complicated in comparison
with that calculated within the exchange approximation. A new type of domain walls (three-layered domain walls) is predicted
to arise due to frustrations. It is shown that domain walls in the antiferromagnetic interlayer are switched when the parallel
orientation of the magnetization vectors of the ferromagnetic layers changes to the antiparallel one.
This article reviews the recent advances of epitaxial ferromagnetic thin films and heterostructures as well as devices towards semiconductor-based spin-electronics or often called spintronics. We review the developments of III–V based ferromagnetic thin films and heterostructures grown by molecular beam epitaxy, with focus on the Mn-delta-doped GaAs/p-AlGaAs heterostructures with high ferromagnetic transition temperature, and control of the spin-dependent properties. As a new direction in spintronics research, we present our recent study on a new silicon-based spin device, spin metal-oxide-semiconductor field-effect transistor (spin MOSFET), and novel reconfigurable or reprogrammable logic gates using spin MOSFETs, which are compatible with the current CMOS technology and promising for reconfigurable computing.
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Usp. Fiz. Met. 8, 247 (2007).
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Black Sea Coast, Zatoka, Odesa region, Ukraine
10-15th of September 2017
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which will be spent from May, 16th till May, 18th, 2018 on the basis of the Sumy State University. More information http://aist.sumdu.edu.ua
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The heats of formation in the condensed phase of 1:2 complexes of CuCl2 and CuBr2 with diethyl, di-n-propyl, di-n-butyl, di-iso-butyl and dibenzylamines have been measured using a reaction calorimeter. The heats of formation of the complexes do not vary significantly with the nature of the alkyl substituent on the amine except for the dibenzylamine complexes which have considerably smaller heats ... [Show full abstract] of formation. CuBr2 shows better acceptor property than CuCl2 towards the amines.
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