Zero-field-cooling exchange bias up to room temperature in the strained kagome antiferromagnet Mn3.1Sn0.9.

Zero-field-cooling exchange bias (ZFC EB) has always been a research hotspot for researchers, because it can realize the movement of the magnetization hysteresis loop along the field axis without field cooling, which greatly expands the universality and convenience of the application of the exchange bias effect. Achieving ZFC EB at room temperature is an ongoing challenge. To this end, a design strategy from the sublattice level is proposed, and a wide temperature range ZFC EB up to room temperature with a vertical magnetization shift is observed in the strained kagome antiferromagnet Mn3.1Sn0.9. Magnetic analysis and first-principles calculations reveal that the ZFC EB arises from the strong exchange interaction between the non-coplanar antiferromagnetic Mn kagome sublattice occupying normal Mn sites and the collinear ferromagnetic Mn sublattice occupying Sn sites. This discovery is of great significance for the application of ZFC EB in antiferromagnetic spintronic devices.

Influence of the type of carrier on ferromagnetism in a Si semiconductor implanted with Cu ions.

Silicon semiconductor samples implanted with Cu ions and samples co-implanted with Cu- and N-ions were prepared by MEVVA and the Kaufman technique. None of the samples showed evidence of secondary phases. The initially n-type Si matrix, when implanted with Cu ions, changed to a p-type semiconductor, and the Cu ions existed as local Cu2+ cations in the p-type environment. As a result, none of the Cu-implanted samples were ferromagnetic at room temperature. The co-implanted samples, on the other hand, showed room-temperature ferromagnetism because the introduction of N ions made the carrier type change from p-type to n-type which is favorable for the appearance of Cu2+. First principles calculations were applied to understand the experimental phenomena. The formation energy was reduced by implanting N ions, and was decreased effectively with the increase in ratio of N to Cu ions. The density of states and spin density of states indicated that the hybridization of s, p and d electrons induced ferromagnetism at 0 K. Particularly, we proposed possible exchange interactions between the Cu2+-N-(N4+)-Cu2+ ions to explain the ferromagnetism mechanism.

Magnetic properties of Al-SiC co-sputtered films grown by radio frequency sputtering.

Room-temperature ferromagnetism was observed in the Al-SiC co-sputtered films fabricated by radio frequency (RF) sputtering. When the annealing temperature (Ta) was increased from 800 to 1100 degrees C, the ferromagnetic ordering was present with the formation of Al-C bonds. Both annealing and Al-doped the films can improve the crystallization of SiC and induce long-range magnetic order in the Al-SiC co-sputtered films. Experiments show that the Al solubility was less than 0.8 at% in SiC matrix. As a possible explanation for the existence of local magnetic moment in Al-doped SiC, unpaired spins arise in a conversion from sp3 to the sp3/sp2 hybridization. The partial Si-C bonds in SiC were converted to Al-C bonds when the trivalent aluminum entered into Si sites. Al atoms introduce some net spins in Al doped film with the calculated integrated spin density 0.467 microB. The structural defects produced by Al-doping have provided an exciting possibility of nonmagnetic atoms-doped to control the spin moments and induce ferromagnetism in wide-gap semiconductor.