The interaction between localized spin-wave modes

CONFERENCE ON LOCALIZED EXCITATIONS IN SOLIDS

xli

where the frequency of bocal vibration ex-

modes and one p-like localized mode,

ceeds considerably the maximum frequency

whose energies may lie above or within

of crystal

THE RELAXATION OF THE LOCAL VIBRONIC EX-

the spinwave band depending upon the magnitude of the impurity spin and its coupling to the host. We have calculated

CITATION IN SOLIDS E.D. Trifonov (Department of Physics,Len— ingrad State University, Leningrad,USSR)

the eigenvalues of the p—like modes when two such impurities are present. In the

A local mode having unharmonic coup— ling with the crystal modes is consider-

case where the single impurity mode lies outside the spinwave band we now find two

ed, The Hamiltonian of the unharmonic int~raction is chosen to have the form

modes symmetrically located with respect to this original mode. This mode split—

H’=~!~a a a’~ + C.C. where a ,a are an— V nihilation operators for the crystal nodes

ting defines an effective impurity—im— purity interaction which we find is pro—

and a~ is the creation operator for the local mode, It is shown that in the case

portional to the overlap at the localized mode wavefunctions, Since the modes be—

T~Othe muster equation for the local

come more localized

mode can be easily solved. Tile decay of a given energy state “n” is descri bed by

from the spinwave band this implies that the interaction is very short range un—

the binomial distribution. The probabil— ity that at the time “t” we shall have the local mode in the quantum state ‘rn” is 6 (~)=C~’(l_e”~’t)m e_’~’tth_m), where mm ~“ n 2 ~ IBVI 6(ui~+w~-w, 6),~ are frequencies of the crystal and local nodes

less the modes are very close to the band. When the single impurity mode lies with— in the band it is characterized by a re— distribution of the density of states, ~We have investigated this redistribution for the case of two impurities.

correspondingly. In particular, we see that the lifetime of arbitrary energy st— ate of the local mode is inverse to its quantum number. In conclusion, a quantum-

STUDY OF THE RESONANT PHONON SCATTERING IN KC1:Li USING THE SPIN—PHONON INTER— ACTION* D. Walton (Solid State Division, Oak Ridge National Laboratory, Oak Ridge,

vibrations,

as they move away

mechanical perturbation method which is equivalent to the muster equation approx— imation is developed.

Tennessee) In a magnetic field, a crystal which

THE INTERACTION BETWEEN LOCALIZED SPINWAVE MODES

conductivity. This effect may be described as an effective removal of heat

Robert M. White and C. Michael Hogan(Department of Physics, Stanford University, Stanford, California)

carriers

The pesence of an impurity spin in a one-dimension Eeisenberg ferromagnet can give rise to two s—hike localized

contains magnetic ions will exhibit a field—dependent decrease in the thermal

from a narrow band in the phon-

Spectrum which is centered about the Larmor frequency for the spins. The

Ofl

spectrum of heat carriers and hence the frequency dependence of the total phonon