Novel spin state in Co akermanite

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K05145
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Osaka University
• Principal Investigator: AKAKI MITSURU 大阪大学, 理学研究科, 特任助教(常勤) (60610904)
• Co-Investigator(Renkei-kenkyūsha): MASUDA Takatsugu 東京大学, 物性研究所, 准教授 (90313014) ; KOHAMA Yoshimitsu 東京大学, 物性研究所, 准教授 (90447524) ; KIHARA Takumi 東北大学, 金属材料研究所, 助教 (80733021)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: マルチフェロイック / 電気磁気効果 / パルス強磁場 / 電子スピン共鳴 / スピン四極子

Outline of Final Research Achievements

Exotic spin-multipolar ordering in spin transition metal insulators has so far eluded unambiguous experimental observation. A less studied, but perhaps more feasible fingerprint of multipole character emerges in the excitation spectrum in the form of quadrupolar transitions. Such multipolar excitations are desirable as they can be manipulated with the use of light or electric field and can be captured by means of conventional experimental techniques. Here we study single crystals of multiferroic Sr2CoGe2O7, and observe a two-magnon spin excitation appearing above the saturation magnetic field in electron spin resonance (ESR) spectra. Our analysis of the selection rules reveals that this spin excitation mode does not couple to the magnetic component of the light, but it is excited by the electric field only, in full agreement with the theoretical calculations. Due to the nearly isotropic nature of Sr2CoGe2O7, we identify this excitation as a purely spin-quadrupolar two-magnon mode.

Free Research Field

強磁場物性