CrCl_(3)隧穿磁阻的界面效应与多场效应调控

Tuning magnetoresistance of chromium chloride tunnel junction through the interface and multi-field effect

磁隧道结是研究磁性材料自旋结构、输运特性、磁相变和磁各向异性的重要实验平台.本研究基于干法转移技术制备了以机械剥离的少层范德瓦耳斯反铁磁绝缘体三氯化铬(CrCl_(3))为势垒层、少层石墨烯为电极的磁隧道结原型器件结构,并进行了低温电磁输运测量,除观测到自旋过滤效应引起的隧穿磁阻外,还发现多种由非传统效应引起的磁阻变化.基于对隧道结自旋结构和能带结构的分析,本文将之归因于由磁近邻效应引起的隧穿机制改变,以及石墨烯电极态密度在高磁场下出现的量子振荡行为.本文报道了在二维磁隧道结中与隧穿磁阻相关且此前未被广泛关注的物理现象,加深了对此类二维异质结构中载流子输运特性的理解,为二维磁性材料的物理性质研究及其自旋电子学应用拓展了新的途径.

Magnetic tunnel junctions(MTJs)serve as essential platforms for investigating spin transport properties,magnetic phase transitions,and anisotropy in magnetic materials.Recently two-dimensional van der Waals antiferromagnetic insulators like chromium chloride(CrCl_(3))or chromium iodide(CrI_3)have been used to develop spin-filtering magnetic tunnel junctions(sf-MTJs),improving the device performance for material property exploration and spintronic applications.However,it is crucial to recognize that the spin-filtering effect is not the sole determining factor of tunneling magnetoresistance(TMR)in these junctions;the interface magnetic exchange intera.ctions and adjustable electrode density of states(DOS)fluctuations,response to applied electric or magnetic fields,can also influence the tunneling current.In this study,we fabricate MTJ devices by using mechanically-exfoliated few-layer CrCl_(3) as the tunnel barrier and few-layer graphene(FLG)as electrodes through dry transfer technique.Conducting low-temperature quantum transport measurements,we observe unconventional TMR behaviors,including bias-volt age-dependent TMR,oscillatory tunneling current under high magnetic fields,and tunable tunneling current via gate voltage.A qualitative model of elastic tunneling current is employed to analyze the spin and band characteristics of the MTJ device.The observed bias-voltage-dependent TMR is attributed to the changes in the tunneling mechanism due to magnetic proximity effect,which induces magnetization in the FLG electrode near the FLG/CrCl_(3) interface.The antiparallel alignment of polarized spin to CrCl_(3)'s magnetization results in injected charge carriers facing a higher tunnel barrier,leading to negative TMR at lower bias voltages.As the bias voltage increases,the magnetic proximity effect lessens,and the device reverts to its conventional spin-filtering functionality.The oscillatory tunneling current is explained by the graphene electrode's quantum oscillatory density of states behavior under vertical magnetic fields,which can be controlled by the applied gate voltage.This study contributes to the understanding of previously unexplored TMR phenomena in two-dimensional MTJs,deepening our insights into carrier transport properties in these heterostructures and broadening avenues for investigating the physical properties of two-dimensional magnetic materials and their spintronic applications.