Cross relaxation and spin thermodynamics in some diluted copper tutton salts

The dynamics of spin systems in some diluted copper Tutton salts is investigated with the method of pulsed ENDOR. This method is suited particularly to study the fast time-dependent behaviour of the spin temperatures. The dynamics in copper Tutton salts is explained with the introduction of four electron Zeeman systems, one combined electron dipole- dipole and proton Zeeman system and the lattice each with a temperature of its own. The cross-relaxation mechanism is a contact between the electron Zeeman systems and the electron dipole-dipole system. Its rate τ⁻¹_cr can be measured directly. Moreover information is gained about the contact between the proton Zeeman system and the electron dipole-dipole system. The experiments demonstrate that the model of a spherical diffusion barrier, that is often used in the theory of the relaxation of the proton magnetization by paramagnetic impurities, is not valid in our samples.