Superconductivity and magnetism of Sm1.85−xGdxCe0.15CuO4−δ and Gd2−yCeyCuO4−δ crystals

Abstract

The magnetism and superconductivity of Sm1.85−xGdxCe0.15CuO4−δ and Gd2−yCeyCuO4−δ crystals were investigated. In the Sm1.85−xGdxCe0.15CuO4−δ system, superconductivity is suppressed by Gd substitution, and temperature-induced magnetic transitions appear at 3, 7, and 135 K above x=1.2 Cu spins have an antiferromagnetic (AF) order along the [110] direction among these transitions, and a weak-ferromagnetic (WF) moment due to a canting of Cu spins appears along the [1¯10] direction at T<~3K and 7K<~T<~135K. The AF order at 3K<~T<~7K changes into a canted spin configuration via field-induced spin reorientation and induces the WF moment. The Néel temperature TNCu (135 K at x=1.2) and spin-reorientation temperature TSR (7 K at x=1.2), which are due to the Cu sublattice and are observed at low field intensity, increase with increasing x. Sm spins have an antiferromagnetic order along the [001] direction at x=0 below the Néel temperature TNR (∼5 K), but TNR, which is observed for low x at high field intensity, decreases with increasing x and disappears at x≈1. Gd spins have an antiferromagnetic order along the [1¯10] direction for specimens with x>1.4 near 3 K. The change in the geometry of rare-earth and Cu spins resulting from Gd substitution is considered to be the reason for the suppression of superconductivity.

Source-reported materials — not catalogue approval

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