외부 자기장에 의한 Tb3Fe5O12의 자기스핀 재배열과 격자 변형

Magnetic Spin Reorientation and Lattice Distortion in Tb3Fe5O12 under External Magnetic Field

Fe₅O₁₂ 에서 외부자기장 (μ₀H = 0, 0.8T)을 가해주면서 8.8K ~ 103K 온도 범위에서 중성자회절 실험을 하였다. 자기장에 의해 canted 자기스핀의 재배열과 격자의 변형을 분석하였다. magneto-dielectrric 효과는 magnetostriction이 아닌 spin-lattice coupling에 의해 발생하는 것으로 분석되었다. spin-lattice coupling은 Fe-Tb 결합길이 변화, 산소 octahedron 회전 등으로 인해 큰 magneto-dielectric effect △ε/ε를 일으킨다.

The evolutions of lattice distortions along with the re-orientation of canted magnetic spins in the Tb₃Fe₅O₁₂ under external magnetic field μ₀H = 0.8T have been characterized by means of neutron diffraction over the temperature range 8.8K ~ 103K. Neutron data were collected from the pure polycrystalline Tb₃Fe₅O₁₂ sample at 8.8K, 65K, and 103K at zero field and at μ₀H = 0.8T. We suggest that the large magneto-dielectrric effect in Tb₃Fe₅O₁₂ originates from prominent spin-lattice coupling by external field: not from the magnetostriction produced by applying magnetic field. This spin-lattice coupling leads to the structural modifications such as, Fe-Tb bond distance, oxygen octahedron rotation, which give rises to a microscopic increase of ionic polarizability and a large magneto-dielectric effect △ε/ε in Tb₃Fe₅O₁₂.