Peculiar Magnetism of the Sm(1−x)GdxTiO3 System

Abstract

Magnetic susceptibility measurements were made on polycrystalline samples of the system Sm(1−x)GdxTiO3 (0.10≤x≤1.0) and on single-crystal GdTiO3. A systematic decrease in the magnetic ordering temperature with increasing x<0.5, falling below 5 K at x=0.5 and increasing with x>0.5, was interpreted to signal a competition between antiferromagnetic and ferromagnetic coupling among itinerant π* electrons of the TiO3 array. In a field H>1 kOe, GdTiO3 approached saturation with a moment of 6 μB/formula unit, consistent with collinear-spin ferrimagnetism. Semicovalent exchange was invoked to justify the observed antiferromagnetic coupling between Gd(III) and Ti(III) spins. However, the M–H curves taken in ±50 kOe were unusual; they were essentially anhysteretic with no measurable remanence or coercivity, but a small ferromagnetic component observed in 20 Oe was typical of a weak, canted-spin ferromagnetism on an antiferromagnetic TiO3 array. The lack of hysteresis and the approach to a ferrimagnetic saturation in high magnetic fields was found for all x for small as well as high applied fields. Although the TiO3 array orders antiferromagnetically below a critical temperature, a ferromagnetic moment was induced on the TiO3 array by an applied magnetic field and by the molecular field associated with antiferromagnetic Gd–Ti interactions. The applied H required to saturate the ferromagnetic moment on the TiO3 array decreased with increasing x.