TY - JOUR
T1 - Critical behavior of amorphous magnets
AU - Aharony, Amnon
PY - 1975
Y1 - 1975
N2 - Renormalization-group techniques are applied to a model Hamiltonian recently proposed by Harris, Plischke, and Zuckermann for the description of amorphous magnets. In this model, a single-ion uniaxial anisotropy, with a random direction of the axis of anisotropy, is introduced. Averaging over this random variable yields an (translationally invariant) effective Hamiltonian, in which the m-component spin variable is replaced by an nm-component vector, and n is finally set equal to zero. Contrary to the result for an isotropic random perturbation, the fixed-point describing the nonrandom m-component critical behavior is unstable with respect to terms in the Hamiltonian generated by the randomness, the appropriate crossover exponent being given exactly by (2φm-2+αm), where φm is the Fisher-Pfeuty anisotropic spin crossover exponent and αm is the specific-heat exponent. Depending on the distribution function for the random anisotropy directions, there are seven or thirteen other fixed points. Most of these are unstable, and the recursion relations probably yield a "runaway" which is interpreted as a smeared transition. Experiments on amorphous TbFe2 are discussed.
AB - Renormalization-group techniques are applied to a model Hamiltonian recently proposed by Harris, Plischke, and Zuckermann for the description of amorphous magnets. In this model, a single-ion uniaxial anisotropy, with a random direction of the axis of anisotropy, is introduced. Averaging over this random variable yields an (translationally invariant) effective Hamiltonian, in which the m-component spin variable is replaced by an nm-component vector, and n is finally set equal to zero. Contrary to the result for an isotropic random perturbation, the fixed-point describing the nonrandom m-component critical behavior is unstable with respect to terms in the Hamiltonian generated by the randomness, the appropriate crossover exponent being given exactly by (2φm-2+αm), where φm is the Fisher-Pfeuty anisotropic spin crossover exponent and αm is the specific-heat exponent. Depending on the distribution function for the random anisotropy directions, there are seven or thirteen other fixed points. Most of these are unstable, and the recursion relations probably yield a "runaway" which is interpreted as a smeared transition. Experiments on amorphous TbFe2 are discussed.
UR - http://www.scopus.com/inward/record.url?scp=0000359165&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.12.1038
DO - 10.1103/PhysRevB.12.1038
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:0000359165
SN - 0163-1829
VL - 12
SP - 1038
EP - 1048
JO - Physical Review B
JF - Physical Review B
IS - 3
ER -