Neutron-scattering study of an Ising antiferromagnet above the percolation threshold: Random-field-induced spin-glass-like behavior inFe0.31Zn0.69F2
| Autor: | R. W. Erwin, F. C. Montenegro, Wm. E. Murray, V. Jaccarino, D. P. Belanger, A. R. King |
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| Rok vydání: | 1991 |
| Předmět: | |
| Zdroj: | Physical Review B. 44:2161-2168 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.44.2161 |
| Popis: | Neutron-scattering studies (elastic and quasielastic) have been made on ${\mathrm{Fe}}_{0.31}$${\mathrm{Zn}}_{0.69}$${\mathrm{F}}_{2}$, both at H=0 and in fields H\ensuremath{\le}5 T collinear with the unique axis. (For the ${\mathrm{Fe}}_{\mathit{x}}$${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Fe}}_{2}$ system ${\mathit{x}}_{\mathit{p}}$=0.24.) The H=0 state exhibits antiferromagnetic (AF) long-range order (LRO) and characteristic random-exhange-Ising-model (REIM) critical behavior, but the degree of ordering is a function of the rate of cooling through the transition ${\mathit{T}}_{\mathit{N}}$\ensuremath{\approxeq}19.8 K. This is indicative of strong dynamical effects on the approach to equilibrium. Two field regions are to be distinguished. For 0H1.5 T the transition to AF LRO exhibits REIM--to--random-field-Ising-model (RFIM) crossover scaling behavior, in both the transition temperature ${\mathit{T}}_{\mathit{c}}$(H) and the equilibrium boundary ${\mathit{T}}_{\mathrm{eq}}$(H). However, entirely new behavior is found as H increases further, unlike any previously seen at large Fe concentrations. For Hg2 T, no AF LRO is observed below ${\mathit{T}}_{\mathrm{eq}}$(H), which now exhibits a field scaling characteristic of the de Almeida--Thouless equilibrium boundary found in exchange-frustrated spin glasses. The observed field scaling, ${\mathit{T}}_{\mathit{N}}$-${\mathit{T}}_{\mathrm{eq}}$(H)\ensuremath{\approxeq}${\mathit{H}}^{2/\mathrm{\ensuremath{\varphi}}}$, is in accord with the more precise Faraday-rotation determination of the crossover exponents \ensuremath{\varphi}=1.42 and 3.4 in the respective low- (H1.5 T) and high- (Hg2 T) field regions. The nature of the random-field-induced spin-glass-like behavior in the region between ${\mathit{T}}_{\mathit{c}}$(H) and ${\mathit{T}}_{\mathrm{eq}}$(H), seen here in a non-exchange-frustrated system, as manifest in its field cycling and time-dependent properties, is reported and analyzed. |
| Databáze: | OpenAIRE |
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