Study of quantum phase transition in antiferromagnetic alternating chain

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K05150
• 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: National Institute for Materials Science
• Principal Investigator: Hase Masashi 国立研究開発法人物質・材料研究機構, 先端材料解析研究拠点, グループリーダー (40281654)
• Research Collaborator: Kohno Masanori
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 反強磁性交替鎖 / 量子相転移 / 混晶 / スピンギャップ / 中性子非弾性散乱 / 磁化

Outline of Final Research Achievements

We investigated the magnetism of spin-3/2 antiferromagnetic alternating chain compounds RCrGeO5 (R = Ho, Er or Nd) and NdCrTiO5 using magnetization and neutron-scattering measurements. The compounds as well as already known R = Y or Sm compounds have a strongly dimerized ground state. We were not able to find a compound with a weakly dimerized ground state.
We also studied antiferromagnetic spin cluster compounds. We found a small magnetic moment in CuInVO5, reduction of the magnetic moment by quantum fluctuation in FeVMoO7 in spite of spin-5/2, and unstable ordered state in 0 T in Rb2Ni2Mo3O12 like an order in the vicinity of a quantum critical point.

Free Research Field

数物系科学

Academic Significance and Societal Importance of the Research Achievements

RCrGeO5 (R = Y, Sm, Ho, Er, Nd)とNdCrTiO5の研究の結果、2つのCrスピン間に働く交換相互作用の大きさがCr-Cr距離にとても強く依存することが分かった。Cr-Cr距離が少しでも長くなると、交換相互作用が急激に小さくなるため、これらの物質の2種類の交換相互作用の大きさが大きく異なり、ボンド交替が弱いダイマー基底状態が実現できなかった。
量子臨界点近傍の秩序は通常、圧力や磁場を加えて初めて現れる。Rb2Ni2Mo3O12では、大気圧下のゼロ磁場でも、量子臨界点近傍の秩序が可能なことが分かった。