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Paramagnetic Spin Relaxation Due to Spin–Spin Interaction Assisted by Spin–Phonon Interaction or Vice Versa (I)
Author(s) -
Srivastava K. K. P.,
Singh H. C.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221010103
Subject(s) - paramagnetism , condensed matter physics , phonon , relaxation (psychology) , spin (aerodynamics) , spin wave , spin–lattice relaxation , excited state , chemistry , ferromagnetism , physics , atomic physics , psychology , social psychology , thermodynamics
The electronic spin–spin relaxation is induced by a dipolar magnetic coupling between the spin states of a pair of paramagnetic ions, whereas the interaction between spin states and lattice vibrations is responsible for the spin–lattice relaxation. Two‐phonon Raman and Orbach spin–lattice relaxation processes are well known where the spin relaxation between a ground doublet proceeds indirectly via transitions to and from an excited state at energy δ with the absorption and emission of two phonons having an energy difference equal to the energy separation between the two states of the ground doublet. In this paper a new type of “mixed spin relaxation process” is considered in which a spin–spin transition is needed to produce effectively an orbit–lattice (i.e. spin–phonon) transition and vice versa. In other words the spin–spin and spin–phonon interactions are simultaneously needed to produce a relaxation transition for this mixed process. A phenomenological approach indicates that the rate of this “mixed spin relaxation process” is proportional to T 4 [exp (δ/KT) + 1] −l (sin k R jl / kR jl ) and this process should proceed very efficiently at low temperatures when the phonon wavelengths are larger than the separation R jl between the paramagnetic ions.