Spin correlations near the ferromagnetic to spin glass crossover. [EuS-SrS; (Fe/sub 1-x/ Mn/sub y/)/sub 75/ P/sub 16/B/sub 6/Al/sub 3/]
We have performed neutron scattering studies of two very different alloys which undergo transitions from ferromagnetic-like (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 1-y/Mn/sub y/)/sub 75/P/sub 16/B/sub 6/Al/sub 3/, an amorphous metal, and their FM-SG multicritical points are at x approx. = 0.50, T=4K and y approx. = 0.35, T=42K 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 re-entrant 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 /sup -/..cap 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 fields which arise when ferromagnetic and spin-glass order parameters are coupled together.
- Research Organization:
- Bell Labs., Murray Hill, NJ (USA); Brookhaven National Lab., Upton, NY (USA); Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Festkoerperforschung; Massachusetts Inst. of Tech., Cambridge (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 5152936
- Report Number(s):
- BNL-34251; CONF-831187-18; ON: DE84007385
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360603* -- Materials-- Properties
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
ALUMINIUM ALLOYS
BEAMS
BORON ALLOYS
CHALCOGENIDES
EUROPIUM COMPOUNDS
EUROPIUM SULFIDES
FERROMAGNETISM
IRON ALLOYS
MAGNETIC PROPERTIES
MAGNETISM
MANGANESE ALLOYS
NEUTRON BEAMS
NUCLEON BEAMS
PARTICLE BEAMS
PHOSPHORUS ADDITIONS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SCATTERING
SPIN GLASS STATE
STRONTIUM COMPOUNDS
STRONTIUM SULFIDES
SULFIDES
SULFUR COMPOUNDS