Structural and Magnetic Properties of Ba_0.7Sr_0.3Ru_1−xMn_xO₃ Hexagonal Perovskites

Abstract

The structures and properties of Ba(0.7)Sr(0.3)Ru(1-x)Mn(x)O(3) perovskites have been investigated in samples prepared at 1300 degrees C in air. Two polytypes are found, a 6H phase for 0.2 < or = x < or = 0.4 and a 4H type for 0.6 < or = x < or = 1. The cell parameters and volume vary linearly in both solid solution ranges. Spin-freezing transitions up to 60 K are observed for the 6H samples, but the 4H materials show high temperature Néel transitions at 210 to 280 K.

Frustrated and Unfrustrated Magnetic Orders in the 10H Perovskite Ba5Sb1−xMn4+xO15−δ

“…A jump in the susceptibility and divergence of ZFC and FC data below 42 K is seen for all samples, but this is characteristic of a trace of the ferromagnetic phase Mn 3 O 4 , below the limit of detection by X-ray diffraction. A further, intrinsic ZFC−FC divergence and a discontinuity or peak in the ZFC susceptibilities mark the second, spin freezing transition when T F < 25 K. Such freezing transitions are observed in other hexagonal manganese oxide perovskites at similar temperatures. , Both magnetic transition temperatures T M and T F increase rapidly with the excess Mn content x , as shown in Figure . The freezing transition shows an approximate T F ∝ x variation, and the T M values are close to the magnitude of the Weiss temperature (Table ).…”

“…The freezing temperatures show an approximate T F ∝ x variation, although the range of available compositions (0.24 < x < 0.36) does not allow other, nonlinear dependencies to be excluded. Monotonic T F ∼ x variations are often observed when x represents the concentration of a magnetic dopant in a nonmagnetic host, e.g., for binary metallic spin glasses or for the doping of Mn into metallic 6H Ba 0.7 Sr 0.3 Ru 1− x Mn x O 3 . However, it is remarkable that a T F ∝ x variation is observed in Ba 5 Sb 1− x Mn 4+ x O 15−δ , where 80% of the possible cation sites are already occupied by magnetic cations and x represents the partial occupation of the remaining 20%.…”

Shift–Twin Option in Eight-Layer Hexagonal Perovskite Niobates Ba8MNb6O24

“…The structural variation of ABO 3 perovskite can be generally predicted in the scheme of tolerance factor t, which is defined as If the tolerance factor takes a value greater than unity, then a hexagonal perovskite structure is usually adopted, and the proportion of hexagonal stacked-layer increases as t increases. 25,26 When t is greater than 1.10, exclusively hexagonal close-packed stacking and face-sharing octahedra are formed, such as the case of 2H-BaMnO 3 . 27 In the eightlayer twinned and shifted hexagonal perovskite structures here, their overall tolerance factors vary within 1.030−1.040 (Figures 7 and 8b), and the ratio of h layers to c layers are the same although they have different stacking sequences of BaO 3 layers.…”

Charge transfer and a magnetic crossover in hexagonalBaRu1−xMnxO3perovskites

“…This is in contrast to the 6H-type Ba 0.7 Sr 0.3 Ru 1−x Mn x O 3 materials where full paramagnetic Mn moments are observed at low dopings. 32 The small fraction of localized spins in the low-doped BaRu 1−x Mn x O 3 series freezes at T F Ϸ 25 K and no x dependence of T F is apparent ͑Fig. 6͒.…”