7 research outputs found
Spin fluctuations in nearly magnetic metals from ab-initio dynamical spin susceptibility calculations:application to Pd and Cr95V5
We describe our theoretical formalism and computational scheme for making
ab-initio calculations of the dynamic paramagnetic spin susceptibilities of
metals and alloys at finite temperatures. Its basis is Time-Dependent Density
Functional Theory within an electronic multiple scattering, imaginary time
Green function formalism. Results receive a natural interpretation in terms of
overdamped oscillator systems making them suitable for incorporation into spin
fluctuation theories. For illustration we apply our method to the nearly
ferromagnetic metal Pd and the nearly antiferromagnetic chromium alloy Cr95V5.
We compare and contrast the spin dynamics of these two metals and in each case
identify those fluctuations with relaxation times much longer than typical
electronic `hopping times'Comment: 21 pages, 9 figures. To appear in Physical Review B (July 2000
Direct Observation of Paramagnons in Palladium
We report an inelastic neutron scattering study of the spin fluctuations in
the nearly-ferromagnetic element palladium. Dispersive over-damped collective
magnetic excitations or ``paramagnons'' are observed up to 128 meV. We analyze
our results in terms of a Moriya-Lonzarich-type spin fluctuation model and
estimate the contribution of the spin fluctuations to the low temperature heat
capacity. In spite of the paramagnon excitations being relatively strong, their
relaxation rates are large. This leads to a small contribution to the
low-temperature electronic specific heat
Strongly enhanced magnetic fluctuations near the quantum critical point of Cr<sub>1-x</sub>V<sub>x</sub> and why strong exchange enhancement need not imply heavy fermion behavior
Inelastic neutron scattering reveals strong spin fluctuations with energies
as high as 0.4eV in the nearly antiferromagnetic metal CrV.
The magnetic response is well described by a modified Millis-Monien-Pines
function. From the low-energy response, we deduce a large exchange enhancement,
more than an order of magnitude larger than the corresponding enhancement of
the low-temperature electronic heat capacity . A scaling relationship
between and the inverse of the wavevector- averaged spin relaxation
rate is demonstrated for a number of magnetically
correlated metalsComment: Submitted to Physical Review Letter