Spin correlations near the ferromagnetic-to-spin-glass crossover (invited)
We have performed neutron scattering studies on two very different alloys which undergo transitions from ferromagnetic (FM) to spin-glass (SG) states as the temperature is reduced. The alloys are Eu/sub x/Sr/sub 1-x/S, a crystalline insulator, and (Fe/sub x/Mn/sub 1-x/)/sub 75/P/sub 16/B/sub 6/Al/sub 3/, an amorphous metal, and their FM-SG multicritical points are at xapprox. =0.50, T = 4 K and xapprox. =0.65, T = 42 K respectively. In spite of the substantial differences between these materials, the neutron scattering data show that their spin correlations are remarkably similar. In particular, for the samples near the multicritical points, a single Lorentzian describes the magnetic scattering very well. Its width kappa corresponds to a ferromagnetic correlation length xi which, as T is reduced, first increases to a value indistinguishable from infinity, and then decreases to a finite value, as expected for a ferromagnet which evolves into a reentrant spin glass. As the Fe or Eu content is raised, the scattering function at low temperatures deviates increasingly from the Lorentzian form, and is better described by a power law Q/sup -alpha/ with 2<..cap alpha..<3. We find no evidence for coexistence of ferromagnetic order with freezing of the transverse spin components, as proposed by Gabay and Toulouse. We argue on general grounds that the zero-field Gabay-Toulouse state cannot exist in real magnets. However, our results can be explained in terms of the random field effects which arise when ferromagnetic and spin-glass order parameters are coupled together.
- Research Organization:
- AT and T Bell Laboratories, Murray Hill, New Jersey 07974
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 5183103
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 55:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
EUROPIUM SULFIDES
NEUTRON DIFFRACTION
PHASE TRANSFORMATIONS
SPIN GLASS STATE
STRONTIUM SULFIDES
ALUMINIUM ALLOYS
BORON ALLOYS
IRON ALLOYS
MANGANESE ALLOYS
PHOSPHORUS COMPOUNDS
CORRELATIONS
FERROMAGNETISM
ORDER PARAMETERS
TEMPERATURE DEPENDENCE
ULTRALOW TEMPERATURE
AMORPHOUS STATE
VERY LOW TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
EUROPIUM COMPOUNDS
MAGNETISM
RARE EARTH COMPOUNDS
SCATTERING
STRONTIUM COMPOUNDS
SULFIDES
SULFUR COMPOUNDS
360104* - Metals & Alloys- Physical Properties
360603 - Materials- Properties