Exchange Bias in CrO2/Cr2O3 Bilayer Thin Films

2006 ◽  
Vol 45 ◽  
pp. 2528-2533 ◽  
Author(s):  
S. Srinath ◽  
N.A. Frey ◽  
H. Srikanth ◽  
G.X. Miao ◽  
A. Gupta
Keyword(s):  
Thin Films ◽  
Magnetic Anisotropy ◽  
Variable Thickness ◽  
Exchange Bias ◽  
Exchange Coupling ◽  
Hysteresis Loops ◽  
Anisotropy Constant ◽  
Effective Magnetic Anisotropy ◽  
Large Anisotropy

We have investigated the exchange bias in CVD grown epitaxial CrO2/Cr2O3 bilayer thin films using hysteresis loops and resonant RF transverse susceptibility. M-H loops indicated an enhanced coercivity without appreciable loop shift and the transverse susceptibility in CrO2/Cr2O3 bilayers revealed features associated with both the ferromagnetic and antiferromagnetic phases. In addition, TS yielded large anisotropy constant (Keff) values depending on the fraction of Cr2O3 present. The large anisotropy fields observed cannot be accounted for by the variable thickness of CrO2 alone and are indicative of possible exchange coupling between CrO2 and Cr2O3 phases that significantly affects the effective magnetic anisotropy.

Inter-granular exchange coupling and magnetic anisotropy of Ta/Ru/Co-23 at%Pt perpendicular thin films with different Ru underlayer thicknesses

Rare Metals ◽  
2016 ◽  
Vol 35 (6) ◽  
pp. 463-470 ◽  
Author(s):  
Na Xiao ◽  
Bo Yang ◽  
Jian-Sheng Wang ◽  
Song Li ◽  
Yu-Ping Ren ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetic Anisotropy ◽  
Exchange Coupling

Interaction of Magnetic Impurities with Surfaces

1997 ◽  
Vol 475 ◽  
Author(s):  
L. Szunyogh ◽  
B.L. Györffy
Keyword(s):  
Thin Films ◽  
Fermi Surface ◽  
Magnetic Anisotropy ◽  
First Principles ◽  
Anisotropy Constant ◽  
Thickness Dependence ◽  
Magnetic Impurities ◽  
First Principles Calculations ◽  
Spin Polarized ◽  
Fe Impurity

ABSTRACTThe interaction of a magnetic (Fe) impurity with the surface of a non-magnetic (Au) semi-infinite host is investigated in terms of fully relativistic spin-polarized first principles calculations. It is shown that the surface induces a magnetic anisotropy on the impurity which is considerably larger than in the bulk. It is also found that the anisotropy constant K(d) is an oscillating function of the distance d between the impurity and the surface with an amplitude which falls as 1/d2 and a period which is determined by the shape of the Fermi Surface of the bulk Au host. However, the question still remains open whether the magnitude of the anisotropy energy is sufficiently large to explain the thickness dependence of the Kondo amplitude B in thin films of dilute FecAu1-c alloys.

scholarly journals Effect of Magnetic Field and Temperature on the Exchange Bias in Phase-Separated Nd1-xSrxCoO3(x=0.10, 0.15)

2015 ◽  
Vol 9 (1) ◽  
pp. 56-59 ◽  
Author(s):  
Yi-Yun Yang
Keyword(s):  
Magnetic Field ◽  
Exchange Bias ◽  
Exchange Coupling ◽  
Hysteresis Loops ◽  
Freezing Temperature ◽  
Solid State Reaction Method ◽  
Conventional Solid State Reaction ◽  
Magnetic Field Axis ◽  
Coexisting Phases ◽  
The Magnetic Field

The exchange bias phenomena of phase-separated Nd1-xSrxCoO3(x=0.10, 0.15) samples were systematically investigated in this paper. The samples were prepared using conventional solid state reaction method. When the NdSrCoO samples cooled down in magnetic field below freezing temperature, the hysteresis loops shifted along the magnetic field axis. Moreover, exchange bias of Nd1-xSrxCoO3 is strongly dependent on the field and the temperature. The influence of magnetic field on the relative ratio of the coexisting phases may be responsible for these behaviors. Therefore, our study confirmed that in phase-separated system, the exchange coupling at the interface between the ferromagnetism clusters and the spin glass regions may induce interfacial exchange anisotropy.

Giant Magnetoresistance in As-Sputter-Deposited Au/NiFe Multilayer Thin Films

1994 ◽  
Vol 343 ◽  
Author(s):  
W. Y. Lee ◽  
G. Gorman ◽  
R. Savoy
Keyword(s):  
Thin Films ◽  
Exchange Coupling ◽  
Giant Magnetoresistance ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Multilayer Films ◽  
Antiferromagnetic Coupling ◽  
Multilayer Thin Films ◽  
Glass Substrates ◽  
Sputter Deposited

ABSTRACTGiant magnetoresistance with low saturation fields (Hs’s) is reported in Au and permalloy (Ni0.82Fe0.18) or Co-doped permalloy multilayer thin films as-deposited on Ta-overcoated Si and glass substrates. A ΔR/R as high as 4.0% with ≈25 Oe Hs was observed at 295 K for the film consisting of 10 layers of 24 Å Au/13 Å Ni0.82Fe0.18 deposited on a 3 Å Ta-overcoated glass at 50 °C. A Hs value as low as ≈20 Oe with a 15% smaller ΔR/R has been observed for the films with a thicker (e.g., 50 Å) Ta underlayer. Magnetic hysteresis loops of these films indicate the presence of antiferromagnetic exchange coupling between the Ni0.82Fe0.18 layers. This exchange coupling is much smaller for the multilayer films without the Ta underlayer, resulting in a 6x smaller ΔR/R and lOx larger Hs observed for these films. Results of x-ray diffraction analysis indicate stronger (111) texturing for the multilayer films with a Ta underlayer, consistent with the stronger antiferromagnetic coupling between the the Ni0.82Fe0.18 layers in the film. The addition of 2–10 % Co moderately increases the ΔR/R value, but also increases substantially the Hs (up to ≈200 Oe).

Tuning the Exchange Bias in NiFe/Fe-Oxide Bilayers by Way of Different Fe-Oxide Based Mixtures Made with an Ion-Beam Deposition Technique

2007 ◽  
Vol 7 (1) ◽  
pp. 265-271 ◽  
Author(s):  
K.-W. Lin ◽  
P.-H. Ko ◽  
Z.-Y. Guo ◽  
H. Ouyang ◽  
J. van Lierop
Keyword(s):  
Exchange Bias ◽  
Exchange Coupling ◽  
Ion Beam ◽  
Hysteresis Loops ◽  
Bottom Layer ◽  
Cross Sectional ◽  
Fe Oxide ◽  
Different Temperatures ◽  
Spin Populations ◽  
Ar Gas

We have investigated the structural and magnetic properties of ion-beam deposited polycrystalline NiFe (25 nm)/Fe-oxide (35 nm) bilayers. A film prepared with an assist beam O2 to Ar gas ratio of 0% during deposition had a bottom layer that consisted of pure b.c.c. Fe (a = 2.87 Å) whereas films prepared with 19%O2/Ar and 35%O2/Ar had either Fe3O4(a = 8.47 Å) or α-Fe2O3 (a = 5.04 Å, c = 13.86 Å) bottom layers, respectively. Cross-sectional transmission electron microscopy revealed a smooth interface between the top nano-columnar NiFe and bottom nano-columnar Fe-oxide layer for all films. At room temperature, the observed coercivity (Hc ∼ 25 Oe) for a film prepared with 19%O2/Ar indicates the existence of a magnetically hard ferrimagnetic Fe3O4 phase that is enhancing the plain NiFe (Hc ∼ 2 Oe) by way of exchange coupling. A significant amount of exchange bias is observed below 50 K, and at 10 K the size of exchange bias hysteresis loops shift increases with increasing oxygen in the films. Furthermore, the strongest exchange coupling (Hex ∼ 135 Oe at 10 K) is with α-Fe2O3 (35%O2/Ar) as the bottom film layer. This indicates that the pure antiferromagnetic phases work better than ferrimagnetic phases when in contact with ferromagnetic NiFe. Hex(T) is well described by an effective AF domain wall energy that creates an exchange field with a (1 − T/Tcrit) temperature dependence. Hc(T) exhibits three distinct regimes of constant temperature that may indicate the existence of different AF spin populations that couple to the FM layer at different temperatures.

Influence of magnetic anisotropy and its distribution on the hysteresis loops upon patterning thin films

2008 ◽  
Vol 104 (11) ◽  
pp. 113907 ◽  
Author(s):  
S. Boukari ◽  
J. Venuat ◽  
A. Carvalho ◽  
J. Arabski ◽  
E. Beaurepaire
Keyword(s):  
Thin Films ◽  
Magnetic Anisotropy ◽  
Hysteresis Loops

Control of the perpendicular magnetic anisotropy and perpendicular exchange bias in CoPt/CoOx thin films

2019 ◽  
Vol 484 ◽  
pp. 320-323 ◽  
Author(s):  
Chunjiao Pan ◽  
Hongyu An ◽  
Takashi Harumoto ◽  
Zhengjun Zhang ◽  
Yoshio Nakamura ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetic Anisotropy ◽  
Exchange Bias ◽  
Perpendicular Magnetic Anisotropy

scholarly journals Exchange Bias in Thin Films—An Update

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 122
Author(s):  
Tomasz Blachowicz ◽  
Andrea Ehrmann
Keyword(s):  
Thin Films ◽  
Exchange Bias ◽  
Hysteresis Loops ◽  
Theoretical Models ◽  
Shell Nanoparticles ◽  
Interface Coupling ◽  
Antiferromagnetic Materials ◽  
New Material ◽  
Experimental Findings ◽  
Core Shell Nanoparticles

The exchange bias (EB) is an effect occurring in coupled ferromagnetic/antiferromagnetic materials of diverse shapes, from core–shell nanoparticles to stacked nanostructures and thin films. The interface coupling typically results in a horizontal—often also vertical—shift of the hysteresis loop, combined with an increased coercivity, as compared to the pure ferromagnet, and the possibility of asymmetric hysteresis loops. Several models have been developed since its discovery in 1956 which still have some drawbacks and some unexplained points, while exchange bias systems are at the same time being used in hard drive read heads and are part of highly important elements for spintronics applications. Here, we give an update of new theoretical models and experimental findings regarding exchange bias phenomena in thin films during the last years, including new material combinations in which an exchange bias was found.

scholarly journals Температурные изменения магнитной структуры мультиферроика BiFe-=SUB=-0.80-=/SUB=-Cr-=SUB=-0.20-=/SUB=-O-=SUB=-3-=/SUB=-

2019 ◽  
Vol 61 (6) ◽  
pp. 1107
Author(s):  
В.С. Русаков ◽  
В.С. Покатилов ◽  
А.С. Сигов ◽  
А.А. Белик ◽  
М.Е. Мацнев
Keyword(s):  
Magnetic Anisotropy ◽  
Temperature Dependence ◽  
Spin Wave ◽  
Easy Axis ◽  
Anisotropy Constant ◽  
Paramagnetic State ◽  
Mössbauer Study ◽  
Magnetic Anisotropy Constant ◽  
Effective Magnetic Anisotropy ◽  
Anharmonicity Parameter

AbstractThe results of a Mössbauer study of the magnetic structure of multiferroic BiFe_0.80Cr_0.20O_3 in the temperature range of 5–550 K are presented. It is found that a collinear antiferromagnetic structure of the G type is present in BiFe_0.80Cr_0.20O_3 at temperatures below 260 K. Above 260 K, an anharmonic spin wave with a magnetic anisotropy of the easy-axis type with a high value of the anharmonicity parameter m arises. With a further increase in the temperature, the m parameter decreases and tends to zero at T ~ 420 K, at which a harmonic spin wave comes into existence. Above a temperature of about 420 K, the m parameter increases again and the spin wave becomes anharmonic with an easy-plane magnetic anisotropy. At the Néel temperature, T _N = 505 ± 10 K, the sample undergoes a transition from the magnetically ordered to the paramagnetic state. The change in the type of magnetic anisotropy at T ~ 420 K is explained by competing contributions of different signs to the effective magnetic anisotropy constant and their different temperature dependence for the BiFe_0.80Cr_0.20O_3 multiferroic.

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