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University of Nebraska - Lincoln

Bias

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Full-Text Articles in Physics

Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Yi Wang, Christian Binek, Peter A. Dowben Jun 2010

Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Yi Wang, Christian Binek, Peter A. Dowben

Christian Binek Publications

Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr2O3 has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr2O3 single crystal, we achieve reversible, room-temperature isothermal switching of the exchange-bias field between ...


Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, Sarbeswar Sahoo, Christian Binek Oct 2008

Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, Sarbeswar Sahoo, Christian Binek

Christian Binek Publications

Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(10 nm)/Cr2O3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T = 5 K to T = 50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T<200K up to the highest measured temperature of T = 395 K. Remarkably, the latter is far above the bulk Néel temperature TN = 307 K. EB training effects occur only at 5 K < T < 50 K. We show that this training can be quenched by subjecting the system to DC magnetic field, µ0HDC <= 7 T. The applied field most likely induces a temperature dependent spin-flop transition. Upon its removal the antiferromagnetic Cr2O3 pinning layer evolves uniformly into its quasi-equilibrium spin configuration thus leading to quasi-equilibrium EB.


Extrinsic Control Of The Exchange Bias, Christian Binek Jan 2004

Extrinsic Control Of The Exchange Bias, Christian Binek

Christian Binek Publications

A new control mechanism for the exchange bias effect in magnetic heterostructures is proposed. It takes advantage of the magnetoelectric effect which takes place in the antiferromagnetic pinning layer. In contrast with the pioneering AC measurements of the magnetoelectric effect, we investigate the magnetic response of the prototypical magnetoelectric compound Cr2O3 on static electric fields. The linear dependence of the magnetic moment on the applied axial electric field and the temperature dependence of the corresponding slopes αshort parallel are measured by DC SQUID magnetometry. The contribution of the field-induced surface magnetization and its impact on the exchange bias effect is ...


Exchange Bias In Fef20-Copt Heterosystems With Perpendicular Anisotropy, Christian Binek Nov 2001

Exchange Bias In Fef20-Copt Heterosystems With Perpendicular Anisotropy, Christian Binek

Christian Binek Publications

The previous exchange bias effect is measured in heterosystems with perpendicular anisotropy consisting of Co/Pt multilayers on top of the (0 0 1) face of a previous FeF2 single crystal. The resulting previous exchange field HE exhibits a strong dependence on temperature and the axial freezing field, HF. Within the framework of an Ising-type model, the HE vs. T as well as the HE vs. HF data are explained in terms of the microscopic spin structure at the interface.


Exchange Bias In Fe0.6zn0.4f2 Heterostructures, Christian Binek Oct 2001

Exchange Bias In Fe0.6zn0.4f2 Heterostructures, Christian Binek

Christian Binek Publications

The previous exchange bias field, He, is measured in Fe0.6Zn0.4F2/Fe heterosystems prepared from Fe layers of 14 and 5 nm thickness which are deposited on top of the compensated (1 1 0) surface of the antiferromagnet. Deviations from a linear dependence of He on the magnetization of the Fe layer are attributed to ferromagnetic domains. Moreover, piezomagnetism and its influence on He are evidenced.


Exchange Bias In A Generalized Meiklejohn-Bean Approach, Christian Binek Aug 2001

Exchange Bias In A Generalized Meiklejohn-Bean Approach, Christian Binek

Christian Binek Publications

A generalized Meiklejohn–Bean model is considered in order to derive an analytic expression for the dependence of the previous exchange bias term field on the layer thickness involved in ferromagnetic/antiferromagnetic heterosystems, on the orientation of the applied magnetic field with respect to the magnetic easy axes and on the quenched magnetization MAF of the antiferromagnetic pinning layer. While MAF is a well-known feature of field-cooled dilute antiferromagnets, it seems to occur quite generally also in pure AF pinning substrates. The new analytic expressions are successfully compared with recent experimental results and Monte Carlo investigations.