Tohoku University, Sendai, Japan
Spin current, a spin counterpart of electric current, refers to a flow of electrons’ spin angular momentum in condensed matter. Spin current has been ignored in electromagnetism in matter for many years, since it disappears in a very short distance, typically at the sub-micrometer scale. However, recent developments in nanotechnology have enabled us to make minute structures. For example, in integrated circuits composed of nanoscale wires, spin current may become as important a quantity as electric current. Spin current can be detected using the inverse spin Hall effect: conversion of spin current into electricity in condensed matter. As a result, a lot of spin-current-related phenomena have been discovered. In my talk, I will guide you around the world of spin current science. First, I will give an introduction to the basic concept of spin current, followed by a review of various phenomena discovered using spin current as a guiding principle, such as spin-Seebeck effects, other spin-caloritronics effects, and spin-mechanics effects. The physics and materials science behind these effects will also be discussed.
Eiji Saitoh received the B.S., M.S., and Ph.D. degrees from the University of Tokyo in 1996, 1998, and 2001, respectively. He was an assistant professor and a lecturer at the Department of Physics and the Department of Physico-Informatics, Keio University. In 2004 he was a visiting scholar at the Cavendish Laboratory, University of Cambridge. In 2009 he became a professor at the Institute for Materials Research, Tohoku University. He is also a professor at the World Premier International Advanced Institute for Materials Research (WPI-AIMR), Tohoku University. He is currently acting as research director of the Exploratory Research for Advanced Technology (ERATO) Spin Quantum Rectification (SQR) project in the Japan Science and Technology (JST) Agency.
Prof. Saitoh has published over 200 technical articles in peer-reviewed journals, including books and review articles, and has given more than 100 invited and plenary presentations at international conferences. He received the Japan Academy Medal in 2011 and the International Union of Pure and Applied Physics (IUPAP) Young Scientist Award in 2009. His current research interest is physics of spintronics and nanoelectronics.
Imagine a future in which food is used to activate specific immune reactions in a human body based on an external noninvasive magnetic stimulus. Dream of a material that stores and releases energy reversibly by temperature changes between day and night. These visions may be realized by using magnetic nanoparticles that are functionalized to be biocompatible, environmentally stable and recyclable, self-healing, and low-cost.
In this presentation I will discuss the basic concepts of magnetic nanomaterials and their magnetic properties with a focus on how to tune specific parameters in a controlled fashion to achieve the dreams of the future. I will highlight state-of-the-art experimental technologies that allow us to understand microscopic properties and interactions in relation to electronic structure changes caused by changes in size, shape, and composition of nanomaterials. Then I will discuss how this understanding is used when nanomagnets are functionalized for targeted drug delivery or composed to form macroscopic materials for new energetic applications like magnetic refrigeration. I will demonstrate that the seemingly complex behavior of hybrid metal/metal, metal/oxide, or oxide/oxide interface materials can be understood from the three fundamental interactions in magnetism: magnetic exchange interaction due to orbital overlap, spin-orbit interaction due to inner- and intra-atomic relativistic corrections (e.g., crystal field effects) and the long-range magnetic dipolar interaction. Several examples will be presented, including the formation of above-room-temperature ferromagnetic interface layers between low-temperature antiferromagnetic layers and the evolution of lattices of magnetic textures (skyrmions) in confined dimensions. The talk will end with an episode in the life of an imaginary golf-playing couple in the year 2040 who use their “Smart Magnet” (SMAG) phone to energize and heal their bodies on the green.