Magnetoelastic and thermal effects in the BiMn2O5 lattice: a high-resolution x-ray diffraction study

High-resolution synchrotron x-ray diffraction measurements were performed on single crystalline and powder samples of BiMn2O5. A linear temperature dependence of the unit cell volume was found between T_{N}=38$K and 100 K, suggesting that a low-energy lattice excitation may be responsible for the lattice expansion in this temperature range. Between T* ~ 65 K and T_{N}, all lattice parameters showed incipient magnetoelastic effects, due to short-range spin correlations. An anisotropic strain along the a-direction was also observed below T*. Below T_{N}, a relatively large contraction of the a-parameter following the square of the average sublattice magnetization of Mn was found, indicating that a second-order spin hamiltonian accounts for the magnetic interactions along this direction. On the other hand, the more complex behaviors found for$b$and$c$ suggest additional magnetic transitions below T_{N} and perhaps higher-order terms in the spin hamiltonian. Polycrystalline samples grown by distinct routes and with nearly homogeneous crystal structure above T_{N} presented structural phase coexistence below T_{N}, indicating a close competition amongst distinct magnetostructural states in this compound.Comment: 23 pages, 7 figure

LARGE-SCALE RESEARCH FACILITIES «MID-LATITUDE GEOPHYSICAL OBSERVATION COMPLEX «MIKHNEVO»

Presented here are the descriptions of the Large-Scale Research Facilities (LSRF) «Mid-latitude complex of geophysical observations "Mikhnevo"» at the Institute of Geospheres Dynamics of the Russian Academy of Sciences. The composition of the measuring complex, equipment and applied techniques are provided. The paper also presents some of the scientific results obtained at the LSRF «Mikhnevo» in recent years

Frozen superparaelectric state of the local polar domains in GdMn2O5 and Gd0.8Ce0.2Mn2O5

This work was supported by RFBR (Grant N 18-32-00241)