磁性絶縁体におけるマグノン-フォノン熱輸送とスピンゼーベック効果

要約のみTohoku University齊藤英治課

Quantitative Temperature Dependence of Longitudinal Spin Seebeck Effect at High Temperatures

This article reports temperature-dependent measurements of longitudinal spin Seebeck effects (LSSEs) in Pt/Y$_3$Fe$_5$O$_{12}$ (YIG)/Pt systems in a high temperature range from room temperature to above the Curie temperature of YIG. The experimental results show that the magnitude of the LSSE voltage in the Pt/YIG/Pt systems rapidly decreases with increasing the temperature and disappears above the Curie temperature. The critical exponent of the LSSE voltage in the Pt/YIG/Pt systems at the Curie temperature was estimated to be 3, which is much greater than that for the magnetization curve of YIG. This difference highlights the fact that the mechanism of the LSSE cannot be explained in terms of simple static magnetic properties in YIG.Comment: 9 pages, 5 figures, 1 tabl

Spin and Spin Current -- From Fundamentals to Recent Progresses

Along with the progress of the spin science and spintronics research, the flow of electron spins, \emph{i.e.}, spin current, has come to attract attention. New phenomena and electronic states were explained one after another using the concept of spin current. Moreover, as many of the conventionally known spintronics phenomena became well organized based on spin current it has rapidly been recognized as an essential concept in a wide range of condensed matter physics. In this article, we focus on recent developments in the physics of spin, spin current, and their related phenomena, where the conversion between spin angular momentum and different forms of angular momentum plays an essential role. Starting with an introduction to spin current, we first discuss the recent progress in the spintronic phenomena driven by spin-exchange coupling: spin pumping, topological Hall torque, and emergent inductor. We then extend our discussion to the interaction/interconversion of spins with heat, lattice vibrations, and charge current and address recent progress and perspectives on the spin Seebeck and Peltier effects. Next, we review the interaction between mechanical motion and electron/nuclear spins and argue the difference between the Barnett field and the rotational Doppler effect. We show that the Barnett effect reveals the angular momentum compensation temperature, at which the net angular momentum is quenched in ferrimagnets.Comment: 23 pages, 18 figure

Regulation of male germline transmission patterns by the Trp53-Cdkn1a pathway

A small number of offspring are born from the numerous sperm generated from spermatogonial stem cells (SSCs). However, little is known regarding the rules and molecular mechanisms that govern germline transmission patterns. Here we report that the Trp53 tumor suppressor gene limits germline genetic diversity via Cdkn1a. Trp53-deficient SSCs outcompeted wild-type (WT) SSCs and produced significantly more progeny after co-transplantation into infertile mice. Lentivirus-mediated transgenerational lineage analysis showed that offspring bearing the same virus integration were repeatedly born in a non-random pattern from WT SSCs. However, SSCs lacking Trp53 or Cdkn1a sired transgenic offspring in random patterns with increased genetic diversity. Apoptosis of KIT⁺ differentiating germ cells was reduced in Trp53- or Cdkn1a-deficient mice. Reduced CDKN1A expression in Trp53-deficient spermatogonia suggested that Cdkn1a limits genetic diversity by supporting apoptosis of syncytial spermatogonial clones. Therefore, the TRP53-CDKN1A pathway regulates tumorigenesis and the germline transmission pattern