The magnetic structure of YMnO₃perovskite revisited

Abstract

The magnetic structure of the orthorhombic perovskite YMnO3 has been investigated. A study on a polycrystalline sample based on neutron diffraction data and magnetization measurements has shown that YMnO3 becomes magnetically ordered below TN = 42 K. In the space group Pnma, the sinusoidal magnetic structure is defined by a (Cx,0,0) mode and characterized by the propagation vector k = (kx,0,0). The kx-component increases from 0.420(4), immediately below the ordering temperature, to 0.435(2) at T = 28.7 K. Below 28 K the kx-component remains unchanged. The sinusoidal spin arrangement remains stable down to 1.7 K; at this temperature the amplitude of the sinusoid is Ak = 3.89(6) µB. YMnO3 is the most distorted perovskite of the RMnO3 series (R = rare earths); the observed sinusoidal magnetic structure is in contrast with those exhibited by the less-distorted members (i.e. LaMnO3), which are commensurate-type antiferromagnetic structures.

Magnetic field effect and dielectric anomalies at the spin reorientation phase transition ofGdFe3(BO3)4

“…This phenomenon, related to the strong single ion anisotropy of rare-earth ions, is not uncommon and it was observed in a number of different compounds involving rareearth ions and d elements. [15][16][17] Depending on the strength of the anisotropy factors, the coupling between the f moments and d spins results in the rotation of the d spins towards the f moments ͑such as in R 2 CuO 4 , R =Pr,Nd,Sm,Eu͒ 15,18 or vice versa ͑e.g., in orthorhombic HoMnO 3 ͒. 16 In rare cases the f-d exchange can result in an in-plane rotation of the d spins as observed in hexagonal HoMnO 3 .…”

“…[15][16][17] Depending on the strength of the anisotropy factors, the coupling between the f moments and d spins results in the rotation of the d spins towards the f moments ͑such as in R 2 CuO 4 , R =Pr,Nd,Sm,Eu͒ 15,18 or vice versa ͑e.g., in orthorhombic HoMnO 3 ͒. 16 In rare cases the f-d exchange can result in an in-plane rotation of the d spins as observed in hexagonal HoMnO 3 . 19 Dielectric anomalies associated with spin reorientation transitions have been observed in several manganites, 7,20 and the significance of the spin-lattice coupling and magnetoelastic effects has been shown.…”

Evaluation of Sr2MMoO6 (M = Mg, Mn) as anode materials in solid-oxide fuel cells: A neutron diffraction study

“…14) with a ¼ 5.6671(1) Å , b ¼ 5.6537(1) Å , and c ¼ 7.9969(2) Å , in agreement with previous reports. 3 In this model, Sr, O1, O2, and O3 atoms are located at 4e positions, Mn at 2d and Mo at 2c sites. Table IV lists the main atomic parameters after the refinement and Table V the anisotropic displacement factors.…”

“…The crystallographic structure of these oxides can be cubic, orthorhombic, or monoclinic, depending on the occurrence of octahedral tilting. 3 Double perovskites have been proposed as good anode materials in SOFC with better fuel flexibility than the usual metal-electrolyte cermets. 4 In particular, the double-perovskite oxides Sr 2 MMoO 6 (M ¼ Mg, Mn) have been recently shown to provide a stable performance as anode of a SOFC operating on H 2 as fuel and a promising performance with CH 4 as fuel.…”

“…We have investigated the thermal evolution of the crystal structure of Sr 2 MMoO 6 (M ¼ Mg, Mn) in the actual working conditions of an anode in a SOFC from "in situ" neutron powder diffraction (NPD) experiments, in complement with thermal expansion measurements under reducing atmosphere. 3 . The mixture of citrate and nitrate solutions was slowly evaporated, leading to organic resins where a random distribution of the involved cations is expected at an atomic level.…”