Magnetic-field -induced structural changes in the electron doped manganites: CaxSm1-xMnO3 (x = 0.8, 0.85)

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We studied the correlation between magnetic, electrical, structural, and magnetostriction properties of the electron doped manganites CaₓSm₁₋ₓMnO₃ (x = 0.85, 0.8). The paramagnetic to antiferromagnetic transition in both the compounds while cooling is accompanied by an abrupt increase of the spontaneous volume thermal expansion (ΔV/V = 0.07 % for x = 0.85 and 0.25 % for x = 0.2). The x = 0.15 exhibits multiple phase separation at 5 K: G-type, and C-type antiferromagnetic phases in orthorhombic (itPnma) and monoclinic (itP2₁it/m) structures respectively. Magnetic study on x = 0.85 also suggest ferromagnetic regions possibly in Pnma structure coexist with the antiferromagnetic phases. The magnetization (M = 1.2 μB) of x = 0.85 does not reach the value expected for the complete alignment of Mn spins even at 12 T and at 12 K. Metamagnetic transitions (C-type to Ferromagnetic) in both compounds are accompanied by contraction of volumes under high magnetic fields. We suggest that a high magnetic field induces itP2₁it/m (high volume) to itPnma (low volume) structural transition. This is also supported by the neutron diffraction study.