High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4$

• Verfasst von: Werner, Johannes [VerfasserIn]
• Verfasst von: Sauerland, Sven [VerfasserIn]
• Verfasst von: Koo, Changhyun [VerfasserIn]
• Verfasst von: Neef, Christoph [VerfasserIn]
• Verfasst von: Pollithy, Anna [VerfasserIn]
• Verfasst von: Klingeler, Rüdiger [VerfasserIn]
• Titel: High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4$
• Verf.angabe: J. Werner, S. Sauerland, C. Koo, C. Neef, A. Pollithy, Y. Skourski, and R. Klingeler
• E-Jahr: 2019
• Jahr: 24 June 2019
• Umfang: 7 S.
• Fussnoten: Im Titel ist die Zahl "4" tiefgestellt ; Gesehen am 06.08.2019
• Titel Quelle: Enthalten in: Physical review
• Ort Quelle: Woodbury, NY : Inst., 2016
• Jahr Quelle: 2019
• Band/Heft Quelle: 99(2019,21) Artikel-Nummer 214432, 7 Seiten
• ISSN Quelle: 2469-9969
• DOI: doi:10.1103/PhysRevB.99.214432
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1670624595

Abstract

We report the magnetic phase diagram of single-crystalline LiFePO4 in magnetic fields up to 58 T and present a detailed study of magnetoelastic coupling by means of high-resolution capacitance dilatometry. Large anomalies at TN in the thermal-expansion coefficient α imply pronounced magnetoelastic coupling. Quantitative analysis yields the magnetic Grüneisen parameter γmag=6.7(5)×10−7 mol/J. The positive hydrostatic pressure dependence dTN/dp=1.46(11) K/GPa is dominated by uniaxial effects along the a axis. Failure of Grüneisen scaling below ≈40K, i.e., below the peak temperature in the magnetoelectric coupling coefficient [7], implies several competing degrees of freedom. A broad and strongly magnetic field dependent anomaly in α in this temperature regime highlights the relevance of structure changes. Upon application of the magnetic field B||b axis, a pronounced jump in the magnetization implies spin reorientation at BSF=32T as well as a precursing phase at 29 T and T=1.5K. In a two-sublattice mean-field model, the saturation field Bsat,b=64(2)T enables assessing the effective antiferromagnetic exchange interaction Jaf=2.68(5)meV as well as anisotropies Db=−0.53(4)meV and Dc=0.44(8)meV.