Figure 1: Inverse, corrected susceptibility for three different PdMn samples.
In magnetic thermometry one measures the susceptibility of a ferromagnetic sample close to its Curie temperature. Due to the diverging character of the susceptibility a high temperature resolution is possible, in particular if the Curie temperature is shifted close to the temperature of interest (2.2 K in the case of superfluid helium).
It turned out that the Curie temperature can be better controlled in the PdMn alloys than in the GaAs/Mn structures. Figure 1 below shows the inverse susceptibility versus temperature for three different PdMn samples. The intercept with the temperature axis gives the Curie temperature of each sample. One can see that for the 0.66 at. % Mn and the 0.45 at. % Mn sample one has Curie temperatures of 2.13 K and 1.95 K, respectively. Thus both samples are well suited for future use in high-resolution thermometry close to 2.2 K.