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Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 9: Cooperative phenomena: Spin structures and magnetic phase transitions

MA 9.8: Talk

Monday, April 1, 2019, 16:45–17:00, H53

Magnetism and magneto-elastic coupling in LiFePO4Johannes Werner1, Sven Sauerland1, Changhyun Koo1, Mahmoud Abdel-Hafiez1,2, Christoph Neef1, Sergei Zvyagin3, and •Rüdiger Klingeler11Kirchhoff Institute of Physics, Heidelberg University, Heidelberg, Germany — 2Physikalisches Institut, Goethe Universität, Frankfurt a.M., Germany — 3High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

We report thermal expansion, magnetostriction, specific heat, static and pulsed-field magnetisation, and antiferromagnetic resonance studies on single-crystalline LiFePO4 [1]. The evolution of long-range antiferromagnetic order at TN= 50.1(5) K which is associated with a significant magnetoelectric effect [2] features pronounced anomalies in the thermal expansion coefficients. Uniaxial pressure effects are positive for pressure along the a- and b-axes and only very small for pc. This behaviour as well as anomalies in α appearing upon further cooling are discussed considering coupling of spin, structure, and dielectric properties. The magnetic phase diagram is mapped out. It features a spin-flop transition at B||b =32 T. Pulsed-field ESR experiments show closing of the AFM gap at BSF. The AFM resonance modes are well described by a mean-field model employing orthorhombic anisotropy, DM interaction, and the excitation gap inferred from recent neutron data [3].

[1] C. Neef et al., J. Cryst. Growth 462, 50 (2017)

[2] R. Toft-Petersen et al., Phys. Rev. B 92, 024404 (2015)

[3] Y. Yiu et al., Phys. Rev. B 95, 104409 (2017)

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