Defect-correlated skyrmions and controllable generation in perpendicularly magnetized CoFeB ultrathin films

APPLIED PHYSICS LETTERS 119:6 (2021) ARTN 062402

Authors:

Haihong Yin, Xiangyu Zheng, Junlin Wang, Yu Zhou, Balati Kuerbanjiang, Guanqi Li, Xianyang Lu, Kaiyu Tong, Yichuan Wang, Jing Wu, Vlado K Lazarov, Richard FL Evans, Roy W Chantrell, Jianwang Cai, Bo Liu, Hao Meng, Yongbing Xu

Deriving the skyrmion Hall angle from skyrmion lattice dynamics

Nature Communications Springer Nature 12 (2021) 2723

Authors:

R Brearton, La Turnbull, Jat Verezhak, G Balakrishnan, Pd Hatton, G van der Laan, Thorsten Hesjedal

Abstract:

Magnetic skyrmions are topologically non-trivial, swirling magnetization textures that form lattices in helimagnetic materials. These magnetic nanoparticles show promise as high efficiency next-generation information carriers, with dynamics that are governed by their topology. Among the many unusual properties of skyrmions is the tendency of their direction of motion to deviate from that of a driving force; the angle by which they diverge is a materials constant, known as the skyrmion Hall angle. In magnetic multilayer systems, where skyrmions often appear individually, not arranging themselves in a lattice, this deflection angle can be easily measured by tracing the real space motion of individual skyrmions. Here we describe a reciprocal space technique which can be used to determine the skyrmion Hall angle in the skyrmion lattice state, leveraging the properties of the skyrmion lattice under a shear drive. We demonstrate this procedure to yield a quantitative measurement of the skyrmion Hall angle in the room-temperature skyrmion system FeGe, shearing the skyrmion lattice with the magnetic field gradient generated by a single turn Oersted wire.

Effect of sodium bicarbonate solution on methyltrimethoxysilane-derived silica aerogels dried at ambient pressure

FRONTIERS OF CHEMICAL SCIENCE AND ENGINEERING (2021)

Authors:

Yujing Liu, Xiao Han, Balati Kuerbanjiang, Vlado K Lazarov, Lidija Siller

Modification of the van der Waals interaction at the Bi2Te3 and Ge(111) interface

Physical Review Materials American Physical Society 5 (2021) 024203

Authors:

K Nawa, D Kepaptsoglou, A Ghasemi, P Hasnip, G Bárcena-González, G Nicotra, Pl Galindo, Qm Ramasse, K Nakamura, B Kuerbanjiang, Thorsten Hesjedal, V Lazarov

Abstract:

We present a structural and density-functional theory study of the interface of the quasi-twin-free grown three-dimensional topological insulator Bi2Te3 on Ge(111). Aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy in combination with first-principles calculations show that the weak van der Waals adhesion between the Bi2Te3 quintuple layer and Ge can be overcome by forming an additional Te layer at their interface. The first-principles calculations of the formation energy of the additional Te layer show it to be energetically favorable as a result of the strong hybridization between the Te and Ge.

Spin-current mediated exchange coupling in MgO-based magnetic tunnel junctions

Physical Review B: Condensed Matter and Materials Physics American Physical Society 103:6 (2021) 064416

Authors:

Lukasz Gladczuk, L Gladczuk, P Dluzewski, K Lasek, P Aleshkevych, Db Burn, G van der Laan, Thorsten Hesjedal

Abstract:

Heterostructures composed of ferromagnetic layers that are mutually interacting through a nonmagnetic spacer are at the core of magnetic sensor and memory devices. In the present study, layer-resolved ferromagnetic resonance was used to investigate the coupling between the magnetic layers of a Co/MgO/Permalloy magnetic tunnel junction. Two magnetic resonance peaks were observed for both magnetic layers, as probed at the Co and Ni L3 x-ray absorption edges, showing a strong interlayer interaction through the insulating MgO barrier. A theoretical model based on the Landau-Lifshitz-Gilbert-Slonczewski equation was developed, including exchange coupling and spin pumping between the magnetic layers. Fits to the experimental data were carried out, both with and without a spin pumping term, and the goodness of the fit was compared using a likelihood ratio test. This rigorous statistical approach provides an unambiguous proof of the existence of interlayer coupling mediated by spin pumping.