Abstract
Multi-functional thin films of boron (B) doped Cr2O3 exhibit voltage-controlled and nonvolatile Néel vector reorientation in the absence of an applied magnetic field, H. Toggling of antiferromagnetic states is demonstrated in prototype device structures at CMOS compatible temperatures between 300 and 400 K. The boundary magnetization associated with the Néel vector orientation serves as state variable which is read via magnetoresistive detection in a Pt Hall bar adjacent to the B:Cr2O3 film. Switching of the Hall voltage between zero and non-zero values implies Néel vector rotation by 90 degrees. Combined magnetometry, spin resolved inverse photoemission, electric transport and scanning probe microscopy measurements reveal B-dependent TN and resistivity enhancement, spin-canting, anisotropy reduction, dynamic polarization hysteresis and gate voltage dependent orientation of boundary magnetization. The combined effect enables H = 0, voltage controlled, nonvolatile Néel vector rotation at high-temperature. Theoretical modeling estimates switching speeds of about 100 ps making B:Cr2O3 a promising multifunctional single-phase material for energy efficient nonvolatile CMOS compatible memory applications.
Highlights
Energy barrier which single domain states[8]. This mechanism has been exploited in voltage-controlled exchange bias (EB) heterostructures fabricated from chromia and an exchange coupled perpendicular anisotropic magnetic thin film such as CoPd9–12
Our work demonstrates that B-doping of chromia creates a single-phase material, which enables voltage-controlled nonvolatile rotation of the Néel vector in zero H-field and CMOS compatible operation temperatures
AFM order and the persistence of magnetoelectricity have been predicted and demonstrated up to T = 400 K in Bdoped chromia[23,27], utilizing the high-TN material in device structures which rely on EB, remains elusive
Summary
Magnetoelectric (ME) antiferromagnets, notably the archetypical ME insulator Cr2O3 (chromia), have long been exploited to realize voltage-controlled spintronic devices[1,2,3]. In contrast to their multiferroic counterparts[4,5], ME antiferromagnets have one spontaneous ferroic order parameter whose temperature (T) dependence determines the T-dependence of the ME response[6]. Domain states can be achieved when their degeneracy is lifted In chromia this is accomplished by simultaneously applying E and H along the easy axis (c-axis) such that the free energy difference. Uncompensated AFM surfaces with equilibrium roughness often have a small interface magnetization
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