Magnetoelastic and thermal effects in theBiMn2O5lattice: A high-resolution x-ray diffraction study

Abstract

High-resolution synchrotron x-ray diffraction measurements were performed on single crystalline and powder samples of BiMn 2 O 5 . A linear temperature dependence of the unit cell volume was found between T N = 38 and 100 K, suggesting that a low-energy lattice excitation may be responsible for the lattice expansion in this temperature range. Between T* ϳ 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.

Crystal chemistry aspects of the magnetically induced ferroelectricity in TbMn2O5and BiMn2O5

“…well as in magnetically ordered nonpolar and polar models of these compounds were calculated with using the program "MagInter". The structural data for TbMn 2 O 5 at room temperature [35] and BiMn 2 O 5 at room temperature [36] and T = 100K [11] were taken for calculations and models development. Besides, in the above calculations we used the ionic radii determined by Shannon Tables 1 and 2.…”

“…The compounds TbMn 2 O 5 [35] and BiMn 2 O 5 [11,36] respectively. Higher values of these AF-contributions result from the fact that the O2 and O3 ions are located in the central one-third part of the space between magnetic ions (l'/l) = 1.…”

Origin of the multiferroicity in BiMn2O5 from first-principles calculations

“…In multiferroics, an impressive example is the RMn 2 O 5 (R¼ La, rare earth, Y and Bi) family of oxides, which are isostructural and contain infinite chains of Mn 4 + O 6 and octahedral sharing edges, linked together by Mn 3 + O 5 and RO 8 units [14][15][16]. These compounds undergo a ferroelectric transition just slightly below the antiferromagnetic (AFM) transition temperature, T N ¼39-45 K [17][18][19][20].…”

Effect of Eu substitution on the crystallographic and magnetic properties of the BiMn2O5 oxide obtained by urea combustion

“…The Eu 3+ substitution at the Bi 3+ site leads to a slight contraction of the unit cell (Table 2) ions that form chains along the c axis [23][24][25] . Two experimental facts are worth to be noticed in Figure 4: firstly, the large difference in magnetization values between both samples, in the ordered state; secondly, the quite constant evolution of the FC magnetization below 20-30 K for the Eu-doped sample.…”