Study of spin-lattice dynamics and transports in frustrated spinel oxides

2015 Fiscal Year Final Research Report

• Project/Area Number: 26800174
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Tohoku University
• Principal Investigator: Tomiyasu Keisuke 東北大学, 理学(系)研究科(研究院), 助教 (20350481)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: スピン分子 / フラストレーション / スピン格子結合

Outline of Final Research Achievements

We carried on with the combination work of neutron scattering and ultrasound measurements on the frustrated spinel oxides with no magnetic order. In ZnFe2O4 without orbital degree of freedom, we observed a molecular spin excitation level at 10 meV (~ 100 K in energy). Elastic constant softens below 100 K, in which the thermal population of this level decreases. In MgV2O4 with orbital degree of freedom, the spin-orbital order vanishes by slightly excess Mg and molecular spin excitations were found. However, the energy structure is described as not a discrete level but a broad distribution from near zero to over 30 meV (~ 300 K in energy). The softening of elastic constant was confirmed below 150 K at least, which will be extended up to 300 K in principle in consideration of the spin excitation energy. Our studies experimentally show that the molecular spin excitations are accompanied with spin-lattice coupling and become source of anomalous phonon properties.

Free Research Field

中性子散乱を中心とする強相関電子系と磁性体研究