Determination of Magnetization Dynamics of the Material with Spin Triplet States under the Action of a Weak Varying Field and Spin-Lattice Interaction in Zero Constant Field

The objective of this investigation was to study both regular and irregular dynamics of spin-triplet states (STSs) in the case of one-photon and one-magnon interactions with the varying magnetic field and the lattice, respectively. The anisotropic regular dynamics of STSs of molecular single crystals in zero constant and weak varying magnetic fields (weakness means the absence of saturation at the steady state and of the nutation at the pulse EPR) directed along the molecular axes, was analytically investigated. The equations were derived for the free motion of the sample magnetization, describing its linear oscillations along that molecular axis, along which its nonzero initial value was created. The tensor of the steady-state dynamical susceptibility to the varying field was found. The result of the action of a short MW pulse on STS was analytically described, containing a periodic dependence on the pulse duration and its detuning. The anisotropic irregular dynamics of electron spin-lattice relaxation (SLR) at its one-phonon mechanism was investigated without the high temperature approximation over the phonon temperature; the SLR rates of the separate transitions of STS were calculated; the corresponding SLR probabilities were written in the form, which supposes the fractal dimensionality d of a lattice; the results with d=4/3 agreed well with the experimental data in STS of the buried tryptophan of ribonuclease T1.