Very low temperature magnetization of two dilute PdMn alloys

A SQUID Magnetometer has been used to measure the temperature dependent magnetization of two dilute alloys of Mn in Pd. Results are presented for temperatures T of 0.01 to 1 Kelvin, for applied magnetizing fields Ha of 0.5 to 600 Oe, for samples containing 255 and 575 atomic ppm of Mn. This dilute alloy system displays a remarkable variation in its properties. For the concentration region under study, PdMn may be described as a giant-moment spin glass. (1) At low field and high temperature, the magnetization M follows a Curie-Weiss law, M = CHa/ (T−ϑ), with positive (ferromagnetic) ϑ values of 31 and 78 mK, respectively. From the Curie constant we obtain a ’’giant’’ effective moment per Mn impurity, p of 11 μB (μB = Bohr magneton). With spin S = 5/2, this gives an effective g value of g = 3.7. (2) From the highest field data we estimate the saturation moment per Mn spin gSμB to be 9 μB; with S = 5/2, this gives g = 3.6 in good agreement. (3) As the temperature is lowered in constant applied field the magnetization becomes independent of temperature, a behavior which is characteristic of the total DC magnetization of a spin glass at low temperatures.