Magnetic Properties of Some Orthoferrites and Cyanides at Low Temperatures

Abstract

The magnetization of some rare-earth orthoferrites and related compounds, and of some iron-group cyanides, has been investigated at temperatures between room temperature and 1.3\ifmmode^\circ\else\textdegree\fi{}K. Some are ferromagnetic, some antiferromagnetic, and some paramagnetic following the Curie-Weiss law.The compounds GdV${\mathrm{O}}_{3}$, GdFe${\mathrm{O}}_{3}$, and ErFe${\mathrm{O}}_{3}$ are apparently antiferromagnetic with N\'eel points of 7.5\ifmmode^\circ\else\textdegree\fi{}, 2.5\ifmmode^\circ\else\textdegree\fi{}, and 4.5\ifmmode^\circ\else\textdegree\fi{}K, respectively. Ordering of the Gd and Er ions at low temperatures is indicated. The compounds NdFe${\mathrm{O}}_{3}$, SmFe${\mathrm{O}}_{3}$, YFe${\mathrm{O}}_{3}$, NdV${\mathrm{O}}_{3}$, PrV${\mathrm{O}}_{3}$, and SmV${\mathrm{O}}_{3}$ show a rapid rise in ferromagnetic moment as the temperature is lowered below about 15\ifmmode^\circ\else\textdegree\fi{}K. GdTi${\mathrm{O}}_{3}$ is ferromagnetic with 0.54 Bohr magneton per molecule.Many of the cyanides of type $A(B{\mathrm{C}}_{6}{\mathrm{N}}_{6})$ are ferromagnetic with magnetic moments of 1 to 4 Bohr magnetons per molecule and Curie points of 3 to 50\ifmmode^\circ\else\textdegree\fi{}K.A null method of measurement is used. Movement of a pendulum in a field gradient is detected with strain gauges and balanced with a coil. In the space containing the specimen and the balancing coil the gradient varies linearly with distance.