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Full-Text Articles in Physics

Voltage Controlled Magnetism In Cr2o3 Based All-Thin-Film Systems, Junlei Wang, Will Echtenkamp, Ather Mahmood, Christian Binek May 2019

Voltage Controlled Magnetism In Cr2o3 Based All-Thin-Film Systems, Junlei Wang, Will Echtenkamp, Ather Mahmood, Christian Binek

Christian Binek Publications

Voltage-control of exchange biases through active selection of distinct domain states of the magnetoelectric and antiferromagnetic pinning layer is demonstrated for Cr2O3/CoPd heterostructures. Progress and obstacles towards an isothermal switching of exchange bias are discussed. An alternative approach avoiding exchange bias for voltage-controlled memory exploits boundary magnetization at the surface of Cr2O3 as voltage-controlled state variable. We demonstrate readout and switching of boundary magnetization in ultra-thin Cr2O3/Pt Hall bar devices where reversal of boundary magnetization is achieved via magnetoelectric annealing with simultaneously applied ±0.5 V and 400 mT electric and magnetic fields.


Dispersion Of Electric-Field-Induced Faraday Effect In Magnetoelectric Cr2o3, J. Wang, Christian Binek Mar 2016

Dispersion Of Electric-Field-Induced Faraday Effect In Magnetoelectric Cr2o3, J. Wang, Christian Binek

Christian Binek Publications

The frequency dependence of the electric-field-induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility α and the antiferromagnetic order parameter η. The relative strength of these contributions is determined by the frequency of the probing light and can be tuned between extreme characteristics following the temperature dependence of α or η. The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3+ crystal-field states. The results allow us to measure voltage-controlled selection, isothermal switching, and temperature dependence of η in a ...


Finite Temperature Effects In Magnetic Materials: Model And Ab Initio Studies, Aleksander L. Wysocki Nov 2009

Finite Temperature Effects In Magnetic Materials: Model And Ab Initio Studies, Aleksander L. Wysocki

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

The understanding of finite temperature behavior of magnetic materials is of vital importance for spintronic applications. In this dissertation different theoretical techniques for studying magnetic thermodynamics of various materials are discussed. Cr2O3 is an antiferromagnetic insulator that was proposed to be a key component of new spintronic devices. The magnetic properties of Cr2O3 were studied using the LDA+U method. Magnetism was found to be very well described by the Heisenberg model. Subsequently, magnetic thermodynamics was explored using quantum pair cluster approximation. Overall, very good agreement with experiment was found for the ground state ...


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.