Voltage-Controlled Antiferromagnetism in Magnetic Tunnel Junctions

Abstract

We demonstrate a voltage-controlled exchange bias effect in CoFeB/MgO/CoFeB magnetic tunnel junctions that is related to the interfacial Fe(Co)Ox formed between the CoFeB electrodes and the MgO barrier. The unique combination of interfacial antiferromagnetism, giant tunneling magnetoresistance, and sharp switching of the perpendicularly-magnetized CoFeB allows sensitive detection of the exchange bias. It is found that the exchange bias field can be isothermally controlled by magnetic fields at low temperatures. More importantly, the exchange bias can also be effectively manipulated by the electric field applied to the MgO barrier due to the voltage-controlled antiferromagnetic anisotropy in this system.

Chemical Structure and Magnetism of FeOx/Fe2O3 Interface Studied by X-ray Absorption Spectroscopy

“…Besides, no noticeable peak or dip features, other than those for Fe or γ-Fe 2 O 3 , were observed in the Fe L-edge XMCD data (Figure 2b) in spite of nonzero nominal Fe valence in FeO x (+2x > 0). This implies that the FeO x most plausibly has negligible FM order, i.e., should be almost an antiferromagnet [30,40,41]. Therefore, to summarize, an AFM FeO x is formed spontaneously between the FM Fe and wFM Fe 2 O 3 layers.…”

SSRL: Single Skyrmion Reconfigurable Logic Utilizing 2-D Magnus Force on Magnetic Racetracks

“…These numbers for current and time will then be inputs of the circuit. The geometric parameters we use for our simulations are listed in Table I, along with material parameters for CoFeB/Pt taken from [15].…”

Enhanced magnetoresistance in perpendicular magnetic tunneling junctions with MgAl2O4 barrier

“…The relatively low TMR of these samples (compared to that of CoFeB/MgO junctions) indicates the MAO barrier still doesn't have the good crystalline structure as that of MgO. 37,42 The low TMR could be related to impurity induced tunneling. 43 At 300°C, the TMR ratios are almost similar for a wide range of top CoFeB thicknesses.…”

“…The film stack was deposited in ultra-high vacuum chamber with a base pressure of 10 -9 Torr, under similar conditions of our previous studies. [35][36][37][38] The metallic layers including Co20Fe60B20 (CoFeB) were deposited by the DC magnetron sputtering at 2 mTorr working pressure. The MAO barrier was deposited in three steps by the RF magnetron sputtering at 1.5 mTorr working pressure.…”