E‐Field Control of Exchange Bias and Deterministic Magnetization Switching in AFM/FM/FE Multiferroic Heterostructures

Abstract

The coexistence of electrical polarization and magnetization in multiferroic materials provides great opportunities for novel information storage systems. In particular, magnetoelectric (ME) effect can be realized in multi­ferroic composites consisting of both ferromagnetic and ferroelectric phases through a strain mediated interaction, which offers the possibility of electric field (E‐field) manipulation of magnetic properties or vice versa, and enables novel multiferroic devices such as magnetoelectric random access memories (MERAMs). These MERAMs combine the advantages of FeRAMs (ferroelectric random access memories) and MRAMs (magnetic random access memories), which are non‐volatile magnetic bits switchable by electric field (E‐field). However, it has been challenging to realize 180° deterministic switching of magnetization by E‐field, on which most magnetic memories are based. Here we show E‐field modulating exchange bias and for the first time realization of near 180° dynamic magnetization switching at room temperature in novel AFM (antiferromagnetic)/FM (ferromagnetic)/FE (ferroelectric) multiferroic heterostructures of FeMn/Ni80Fe20/FeGaB/PZN‐PT (lead zinc niobate–lead titanate). Through competition between the E‐field induced uniaxial anisotropy and unidirectional anisotropy, large E‐field‐induced exchange bias field‐shift up to $ {{{\Delta H_{ex}}}\over{{H_{ex}}}} = 218\%$ and near 180° deterministic magnetization switching were demonstrated in the exchange‐coupled multiferroic system of FeMn/Ni80Fe20/FeGaB/PZN‐PT. This E‐field tunable exchange bias and near 180° deterministic magnetization switching at room temperature in AFM/FM/FE multiferroic heterostructures paves a new way for MERAMs and other memory technologies.

Voltage control of magnetism in multiferroic heterostructures

“…The giant E-field dependence of exchange bias in AFM/FM/FE heterostructures provides great opportunities for realizing electrically deterministic magnetization switching in FeGaB film, which constitutes one important step towards MERAMs, and has great potential in E-field writing of novel spintronics and memory devices [25].…”

Electric-field switching of perpendicularly magnetized multilayers

“…[33][34][35][36][37] Electric-field control of perpendicular magnetic anisotropy (PMA) would open up new prospects for the realization of high-density magnetic memory and logic technologies operating at low energy consumption levels. Attempts to attain this goal have mostly focused on charge accumulation or band shifting in ultrathin ferromagnetic layers with a metal oxide gate dielectric.…”

Probing electric field control of magnetism using ferromagnetic resonance

“…Multiferroic materials with simultaneous ferroelectricity and magnetism provide a pathway to achieving strong magnetoelectric coupling with efficient voltage control of magnetism, and compact and power-efficient electric field-tunable magnetic devices [1][2][3][4] . A variety of 'magnetoelectric-multiferroics' such as magnetic/ferroelectric [5][6][7][8][9][10][11][12] and magnetic/multiferroic [13][14][15][16][17] heterostructures have been investigated, which are providing pathways to novel electric field-tunable radio frequency (RF)/microwave signal processing devices 5 , magnetic field sensors 6 , MERAM devices 7 and voltagetunable magnetoresistance devices 8 .…”

“…Several magnetoelectric coupling mechanisms have been explored to achieve efficient electric field control of magnetism, for example, strain-mediated magnetoelectric coupling [9][10][11][12]18,19 , spin-polarized charge-mediated magnetoelectric coupling [20][21][22][23][24][25] and voltage control of carrier-mediated magnetism in dilute magnetic semiconductors [26][27][28] . Strain-mediated magnetoelectric coupling in thin-film magnetic/ferroelectric heterostructures on substrates can be diminished due to substrate clamping effects 6,18,19 , while spin-polarized charge-mediated magnetoelectric coupling can only be observed in ultra-thin (o1 nm) magnetic thin films [20][21][22][23][24][25] , which puts a limit on its application in real magnetoelectric devices.…”