Neutron-scattering study of an Ising antiferromagnet above the percolation threshold: Random-field-induced spin-glass-like behavior in Fe sub 0. 31 Zn sub 0. 69 F sub 2

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.2161· OSTI ID:5469479

Belanger, D P; Murray, Jr, W E ^[1]; Montenegro, F C; King, A R; Jaccarino, V ^[2]; Erwin, R W ^[3]

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1. Department of Physics, University of California, Santa Cruz, California (USA)
2. Department of Physics, University of California, Santa Barbara, California (USA)
3. National Institute of Standards and Technology, Gaithersburg, Maryland (USA)

Neutron-scattering studies (elastic and quasielastic) have been made on Fe{sub 0.31}Zn{sub 0.69}F{sub 2}, both at {ital H}=0 and in fields {ital H}{le}5 T collinear with the unique axis. (For the Fe{sub {ital x}}Zn{sub 1{minus}{ital x}}Fe{sub 2} system {ital x}{sub {ital p}}=0.24.) The {ital 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 {ital T}{sub {ital N}}{approx}19.8 K. This is indicative of strong dynamical effects on the approach to equilibrium. Two field regions are to be distinguished. For 0{lt}{ital H}{lt}1.5 T the transition to AF LRO exhibits REIM--to--random-field-Ising-model (RFIM) crossover scaling behavior, in both the transition temperature {ital T}{sub {ital c}}({ital H}) and the equilibrium boundary {ital T}{sub eq}({ital H}). However, entirely new behavior is found as {ital H} increases further, unlike any previously seen at large Fe concentrations. For {ital H}{gt}2 T, no AF LRO is observed below {ital T}{sub eq}({ital 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, {ital T}{sub {ital N}}{minus}{ital T}{sub eq}({ital H}){approx}{ital H}{sup 2/{phi}}, is in accord with the more precise Faraday-rotation determination of the crossover exponents {phi}=1.42 and 3.4 in the respective low- ({ital H}{lt}1.5 T) and high- ({ital H}{gt}2 T) field regions. The nature of the random-field-induced spin-glass-like behavior in the region between {ital T}{sub {ital c}}({ital H}) and {ital T}{sub eq}({ital H}), seen here in a non-exchange-frustrated system, as manifest in its field cycling and time-dependent properties, is reported and analyzed.

• DOE Contract Number: FG03-87ER45324
• OSTI ID: 5469479
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 44:5; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ANTIFERROMAGNETISM
COHERENT SCATTERING
CRYSTAL MODELS
DIFFRACTION
FARADAY EFFECT
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
IRON COMPOUNDS
IRON FLUORIDES
ISING MODEL
MAGNETISM
MATHEMATICAL MODELS
NEUTRON DIFFRACTION
SCALING LAWS
SCATTERING
SPIN GLASS STATE
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
ZINC FLUORIDES
ZINC HALIDES