Measurement of the thermodynamic temperature using a paramagnetic thermometric material

It is suggested that thermodynamic temperature $T$ be measured with magnetic susceptibility $\chi$ of a colloid solution of single-domain ferromagnet nanoparticles. The magnetic susceptibility is taken as a thermometric parameter, since $\chi$ and temperature are related by Curie’s law. It is shown that for Curie’s law to be satisfied, the magnetic susceptibility should be determined from the formula $\chi=M\mu_0/B$, where $M$ is the magnetization and $B$ is the mean magnetic induction in the colloid solution. Experimental verification carried out for a magnetite nanoparticle solution in the temperature range 273–373 K shows that when the temperature grows, the Curie constant either remains almost unchanged or increases by several percent. The increase in the Curie constant upon heating can be explained by the decomposition of conglomerates containing nanoparticles with antiparallel magnetic moments.