Magnetic Resonance and Susceptibility of Several Ilmenite Powders

Abstract

Magnetic susceptibility, paramagnetic resonance, and antiferromagnetic resonance have been measured in MnTi${\mathrm{O}}_3$, FeTi${\mathrm{O}}_3$, CoTi${\mathrm{O}}_3$, and NiTi${\mathrm{O}}_3$. Néel temperatures $T_N$ of 65, 56, 37, and 23±2°K, respectively, have been measured. The molar susceptibilities appear to obey a Curie Weiss law with $C_m=4.36,3.37,3.72, \mathrm{and} 1.24$°K, and with paramagnetic Curie temperatures ${\Theta }_p=-219,+32,,-9.3, \mathrm{and} -11\mathrm{}$°K, respectively. The effective spectroscopic splitting factors consistent with this law and with paramagnetic resonance are $g_{\mathrm{eff}}=2.01,2.13,2.83,2.22\mathrm{}\pm 0.01$. The susceptibility of MnTi${\mathrm{O}}_3$ exhibits a broad peak near 100°K rather than a well-defined peak at $T_N$. No antiferromagnetic resonance was observed in FeTi${\mathrm{O}}_3$, and no paramagnetic resonance was observed in FeTi${\mathrm{O}}_3$ or CoTi${\mathrm{O}}_3$. The antiferromagnetic resonant frequencies, extrapolated to 0°K, are 156, 145, and 187 kMc/sec for MnTi${\mathrm{O}}_3$, CoTi${\mathrm{O}}_3$, and NiTi${\mathrm{O}}_3$, respectively. A low-frequency mode of 19.1 kMc/sec was also detected in NiTi${\mathrm{O}}_3$. In the system ${\mathrm{Mn}}_{1-x}{\mathrm{Mg}}_x\mathrm{Ti}{\mathrm{O}}_3$, both ${\omega }_R$ and $T_N$ decrease roughly linearly with $x$ in the range $0<x<\mathrm{}0.075\mathrm{}$.