Unconventional periodicities of the Little-Parks effect observed in a topological superconductor
Not Available
Li, Yufan (ORCID:0000000335959089)↗
Engineering topics
Chien, C. L.
Publications and source records attributed to Chien, C. L..
Vector spin Seebeck effect and spin swapping effect in antiferromagnetic insulators with non-collinear spin structure
Antiferromagnets (AFs) are prospective for next-generation high-density and high-speed spintronic applications due to their negligible stray field and ultrafast spin dynamics, notwithstanding the challenges in detecting and manipulating AF order with no magnetization (M = 0). Among the AFs, non-collinear AFs are of particular interest because of their unique properties arising from the non-collinear spin structure and the small magnetization M. In this work, we describe the recently observed vector spin Seebeck effect in non-collinear LuFeO 3 , where the magneto-thermovoltage under an in-plane temperature gradient, not previously observed, is consistent with the predicted spin swapping effect. Our results shed light on the importance of the non-collinear spin structure in the emerging spin phenomena in non-collinear AFs and offer a new class of materials for AF spintronics and spin caloritronics.
36 MATERIALS SCIENCE↗
Observation of Vector Spin Seebeck Effect in a Noncollinear Antiferromagnet
Spintronic phenomena to date have been established in magnets with collinear moments, where the spin injection through the spin Seebeck effect (SSE) is always along the out-of-plane direction. Here, we report the observation of a vector SSE in a noncollinear antiferromagnet (AF) LuFeO 3 , where temperature gradient along the out-of-plane and also the in-plane directions can both inject a pure spin current and generate a voltage in the heavy metal via the inverse spin Hall effect (ISHE). We show that the thermovoltages are due to the magnetization from canted spins in LuFeO 3 . Furthermore, in contrast to the challenges of generating, manipulating, and detecting spin current in collinear AFs, the vector SSE in LuFeO 3 is readily viable in zero magnetic field and can be controlled by a small magnetic field of about 150 Oe at room temperature. Furthermore, the noncollinear AFs expand new realms for exploring spin phenomena and provide a new route to low-field antiferromagnetic spin caloritronics and magnonics.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Exploiting Spin Fluctuations for Enhanced Pure Spin Current
We demonstrate the interplay of pure spin current, spin-polarized current, and spin fluctuation in 3d Ni x Cu 1–x . By tuning the compositions of the Ni x Cu 1–x alloys, we separate the effects due to the pure spin current and spin-polarized current. By exploiting the interaction of spin current with spin fluctuation in suitable Ni-Cu alloys, we obtain an unprecedentedly high spin Hall angle of 46%, about 5 times larger than that in Pt, at room temperature. Furthermore, we show that spin-dependent thermal transport via anomalous Nernst effect can serve as a sensitive magnetometer to electrically probe the magnetic phase transitions in thin films with in-plane anisotropy. As a result, the enhancement of spin Hall angle by exploiting spin current fluctuation via composition control makes 3d magnets functional materials in charge-to-spin conversion for spintronic application.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Evidence for spin swapping in an antiferromagnet
Antiferromagnetic insulators offer strategic advantages in spintronic applications because of their negligible stray fields and ultrafast magnetic dynamics. Control of their magnetization and readout of their magnetic state are essential for these applications but remain challenging. In this work, we report the electrical detection of room-temperature magnetization switching in the canted antiferromagnetic insulator LaFeO 3 , capped with a Pt or W overlayer. The observation of a large magneto-thermovoltage with an in-plane temperature gradient suggests that the mechanism is the swapping of spin currents in the antiferromagnet. This effect provides a sensitive electrical probe of the tiny net magnetization in the insulator, which can be manipulated by a magnetic field on the order of 10 mT. Our results highlight a new material class of insulating canted antiferromagnets for spintronics and spin caloritronics and suggests a method for the electrical readout of magnetic signals in an antiferromagnetic insulator. Electrical readout of the state of an antiferromagnet is an important goal for spintronic applications. Now, detection of the electrical voltage created by a thermal gradient in a canted antiferromagnet suggests a route for achieving this goal.
42 ENGINEERING↗
Negligible spin–charge conversion in Bi films and Bi/Ag(Cu) bilayers
Spin pumping experiments using ferromagnetic metals have reported highly efficient spin–charge conversion in Bi and at the Bi/Ag interface, possibly due to the inverse Rashba–Edelstein effect. However, longitudinal spin Seebeck effect experiments using the yttrium iron garnet ferrimagnetic insulator in Bi films and Bi/Ag bilayers do not show evidence of appreciable spin-to-charge conversion except the large Nernst signal inherent to Bi. These contrasting conclusions highlight the differences between magnetic metals and magnetic insulators as spin current injectors. Only the detected voltages that adhere to the inverse spin Hall effect of j C = (2e/h)θ SH j S x σ are due to spin currents.
36 MATERIALS SCIENCE↗
Omnidirectional Control of Large Electrical Output in a Topological Antiferromagnet
Not provided.
Chemistry↗
Voltage-controlled spin–orbit torque switching in W/CoFeB/MgO
Voltage control of magnetism and spintronics have been highly desirable but rarely realized. In this work, we show voltage-controlled spin–orbit torque (SOT) switching in W/CoFeB/MgO films with perpendicular magnetic anisotropy (PMA) with voltage administered through SrTiO 3 with a high dielectric constant. We show that a DC voltage can significantly lower PMA by 45%, reduce switching current by 23%, and increase the damping-like torque as revealed by the first- and second-harmonic measurements. These are characteristics that are prerequisites for voltage-controlled and voltage-select SOT switching spintronic devices.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗