Magnetic order, hysteresis, and phase coexistence in magnetoelectric ${\mathrm{LiCoPO}}_4$

Journal Article · 14 September 2017 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.96.104420 · OSTI ID:1396276

Fogh, Ellen ^[1]; Toft-Petersen, Rasmus ^[1]; Ressouche, Eric ^[2]; Niedermayer, Christof ^[3]; Holm, Sonja Lindahl ^[4]; Bartkowiak, Maciej ^[5]; Prokhnenko, Oleksandr ^[5]; Sloth, Steffen ^[1]; Isaksen, Frederik Werner ^[1]; Vaknin, David ^[6]; Christensen, Niels Bech ^[1]

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1. Technical Univ. of Denmark, Lyngby (Denmark)
2. CEA & Univ. Grenoble Alpes, Grenoble (France)
3. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
4. Paul Scherrer Inst. (PSI), Villigen (Switzerland); Univ. of Copenhagen, Copenhagen (Denmark)
5. Helmholtz-Zentrum Berlin fur Materialien und Energie, Berlin (Germany)
6. Ames Lab. and Iowa State Univ., Ames, IA (United States)

Here, the magnetic phase diagram of magnetoelectric LiCoPO₄ is established using neutron diffraction and magnetometry in fields up to 25.9T applied along the crystallographic b axis. For fields greater than 11.9T, the magnetic unit cell triples in size with propagation vector Q = (0,1/3,0). A magnetized elliptic cycloid is formed with spins in the (b,c) plane and the major axis oriented along b. Such a structure allows for the magnetoelectric effect with an electric polarization along c induced by magnetic fields applied along b. Intriguingly, additional ordering vectors Q ≈ (0,1/4,0) and Q ≈ (0,1/2,0) appear for increasing fields in the hysteresis region below the transition field. Traces of this behavior are also observed in the magnetization. A simple model based on a mean-field approach is proposed to explain these additional ordering vectors. In the field interval 20.5–21.0T, the propagation vector Q = (0,1/3,0) remains but the spins orient differently compared to the cycloid phase. Furthermore, above 21.0T and up until saturation, a commensurate magnetic structure exists with a ferromagnetic component along b and an antiferromagnetic component along

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1396276
• Report Number(s): IS-J--9457
• Journal Information: Physical Review B, Journal Name: Physical Review B Journal Issue: 10 Vol. 96; ISSN 2469-9950; ISSN PRBMDO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English