Manipulation of antiferromagnetic(AFM) spins by electrical means is on great demand to develop the AFM spintronics with low power consumption. Here we report a reversible electrical control of antiferromagnetic moments of FeMn up to 15 nm, using an ionic liquid to exert a substantial electric-field effect. The manipulation is demonstrated by the modulation of exchange spring in[Co/Pt]/FeMn system, where AFM moments in FeMn pin the magnetization rotation of Co/Pt. By carrier injection or extraction,the magnetic anisotropy of the top layer in FeMn is modulated to influence the whole exchange spring and then passes its influence to the [Co/Pt]/FeMn interface, through a distance up to the length of exchange spring that fully screens electric field. Comparing FeMn to IrMn, despite the opposite dependence of exchange bias on gate voltages, the same correlation between carrier density and exchange spring stiffness is demonstrated. Besides the fundamental significance of modulating the spin structures in metallic AFM via all-electrical fashion, the present finding would advance the development of low-power-consumption AFM spintronics.
PengXiang ZhangGuFan YinYuYan WangBin CuiFeng PanCheng Song
Recent progress in the electrical control of magnetism in oxides,with profound physics and enormous potential applications,is reviewed and illustrated.In the first part,we provide a comprehensive summary of the electrical control of magnetism in the classic multiferroic heterostructures and clarify the various mechanisms lying behind them.The second part focuses on the novel technique of electric double layer gating for driving a significant electronic phase transition in magnetic oxides by a small voltage.In the third part,electric field applied on ordinary dielectric oxide is used to control the magnetic phenomenon originating from charge transfer and orbital reconstruction at the interface between dissimilar correlated oxides.At the end,we analyze the challenges in electrical control of magnetism in oxides,both the mechanisms and practical applications,which will inspire more in-depth research and advance the development in this field.
Magnetic tunnel junctions （MTJs）, as the seminal spintronic devices, are expected for applications in magne- toresistive sensors due to their large magnetoresistance （MR） and high field sensitivity. Two hybrid Co/insulator/ZnO：Co junctions were fabricated with two different barriers to investigate the magneto-transport properties. Experimental results indicate that, both Co/MgO/ZnO：Co and Co/ZnO/ZnO：Co junctions show the positive and nearly linear MR, and their tunnel magnetoresistances （TMR） are 21.8% and 13.6%, respectively, when the current is applied perpendicular to the film plane under the magnetic field of 2 T at 4 K. The nonlinearity of MR is less than 1% within the magnetic field （H） of 1 kOe 〈 H 〈 12 kOe at low temperature, making them attractive as magnetoresistive sensors. The higher MR of Co/MgO/ZnO：Co junctions is due to the superior spin filtering effect and larger effective barrier height of the MgO barrier. This linear MR characteristic of Co/insulator/ZnO：Co structures shows a promising future on the applications of diluted magnetic semiconductors in magnetoresistive sensors.
Enhancing ion conductance and controlling transport pathway in organic electrolyte could be used to modulate ionic kinetics to handle signals. In a Pt/Poly(3-hexylthiophene-2,5-diyl)/Polyethylene?Li CF3SO3/Pt hetero-junction, the electrolyte layer handled at high temperature showed nano-fiber microstructures accompanied with greatly improved salt solubility. Ions with high mobility were confined in the nano-fibrous channels leading to the semiconducting polymer layer,which is favorable for modulating dynamic doping at the semiconducting polymer/electrolyte interface by pulse frequency.Such a device realized synaptic-like frequency selectivity, i.e., depression at low frequency stimulation but potentiation at high-frequency stimulation.
Siheng LuFei ZengWenshuai DongAo LiuXiaojun LiJingting Luo
