E‐field Control of the RKKY Interaction in FeCoB/Ru/FeCoB/PMN‐PT (011) Multiferroic Heterostructures

Abstract

E-field control of antiferromagnetic (AFM) orders is promising for the realization of fast, compact, and energy-efficient AFM applications. However, as the AFM spins are strongly pinned, the E-field control process is mainly based on the exchange bias regulation that usually confines at a low temperature. Here, a new magnetoelectric (ME) coupling mechanism for the modulation of AFM orders at room temperature is explored. Based on the FeCoB/Ru/FeCoB/(011) Pb(Mg Nb )O -PbTiO (PMN-PT) synthetic antiferromagnetic (SAF) heterostructures, the external E-field generates relative magnetization switching in the two ferromagnetic (FM) layers, leading the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction tuning. This voltage-induced switching behavior can be repeated in a stable and reversible manner for various SAFs, which is a key challenge in the E-field control of AFM coupling and is not resolved yet. The voltage-induced RKKY interaction changes by analyzing the dynamic optical and acoustic modes is quantified, and with first-principles calculations, it is found that the distortion of the Fermi surface by the lattice reconstruction is the key of the relative magnetization switching and RKKY interaction modulation. This voltage control of the RKKY interaction in ME heterostructures provides an easy way to achieve the next generation of AFM/FM spintronic applications.

Electric-field-assisted non-volatile magnetic switching in a magnetoelectronic hybrid structure

“…These experimental results confirm that the magnetic anisotropy is rotated by 90° via the E-field-induced magnetoelastic coupling between the FL and ferroelectric PMN-PT layers, as shown in Figures S13 B and S13C in the supplemental information . Accordingly, the E-field-induced H eff can reversibly rotate magnetization toward 180° with the aid of successively opposite and small H-fields ( Wang et al., 2018a ; Zhao et al., 2016 ). It is mentionable that the physical limit of E-field-induced 180° magnetization reversal lies in how to break the 2-fold symmetry of the degenerate bistable magnetic states of the FL in MTJs/PMN-PT hybrid structures ( Matsukura et al., 2015 ).…”

“…The exchange bias field H eb is estimated to be approximately 470 Oe. Additionally, the magnetization switching of the RL is not modulated by the E-field, as shown in the shaded light green in Figure 8D because the SAF structure provides a strong RKKY interaction for the RL (Wang et al, 2018a(Wang et al, , 2018b. From the magnetic hysteresis loop along the minor axis (the [01-1] direction of the PMN-PT substrate), the magnetic switching becomes easier after applying an E-field of 6 kV/cm, as shown in Figure S13A in the supplemental information.…”

“…Other switching schemes have been proposed based on voltage-controlled magnetic anisotropy manipulation ( Wang et al., 2012 ; Zhao et al., 2018a , 2018b ), magnetoionics ( Bauer et al., 2015 ; Li et al., 2017a , 2017b ; Tan et al., 2019 ), and magnetoelectric effect (ME) ( Li et al., 2014 , 2018 ; Nan et al., 2019 ; Baldrati et al., 2016 ; Chen et al., 2019a ; Lu et al., 2015 ). Among these, the magnetoelectric coupling using multiferroic heterostructures is particularly energy-efficient ( Spaldin and Ramesh, 2019 ; Wang et al., 2018a ; Ghidini et al., 2019 ; Manipatruni et al., 2019 ).…”

Voltage Control of Perpendicular Exchange Bias in Multiferroic Heterostructures

“…The commonly used linear strain effect is proportional to the applied voltage, while the nonlinear strain effect is arising from the 71° and 109° ferroelastic switching which can be generated by a small E‐field near the coercive field . We have measured butterfly‐like strain curve of the PMN‐PT (011) substrate and found that the E‐field induced compressive strain (maximum strain ≈−0.5%) is larger than the tensile strain (maximum strain ≈+0.3%) . This means that the strain effect of the [100] direction can be more remarkable than that of the [01‐1] direction.…”

Oxygen-vacancy induced magnetic phase transitions in multiferroic thin films

“…But, unfortunately, multiferroics are rare in nature, typically present weak magnetoelectric coupling (BiFeO 3 ) 11 , and require extreme thermodynamic conditions for their synthesis (PbVO 3 and BiCoO 3 ) [12][13][14] . In addition, magnetoelectric multiferroics mostly are antiferromagnetic hence potential applications based on external magnetic bias generally are frustrated due to their little influence on antiparallel magnetic spins 15 . Common strategies employed to synthesize bettered multiferroic materials include doping 16,17 , solid solutions 18,19 , and strain engineering 1,20 .…”