Temperature Effect on the Paramagnetic Resonance in Crystals

Temperature effect through Boltzmann· distribution on the position and the shape of parama­ gnetic resonance lines is studied on the assumption that the l~ttice structur2 is rigid. General formulae for the moments of any order ara derived in the form of traces which can be interpreted physically as temperature averages of the quantities represented by the relevant operators. The explicit expressions for the zero-th, the first and the sec')nd moments are given on the basis of the one-ion approximation for the density matrix involved in the temperature average. As examples, applications of the formulae to the case of electronic-paramagnetic resonance in the system of equivalent free ions and to that of nuclear-param~gn etic rsonance in electronic-paramagnetic crystals are discussed.