Spin correlations near the ferromagnetic-to-spin-glass crossover (invited)

Journal Article · Tue Mar 20 04:00:00 EST 1984 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.333426· OSTI ID:5183103

Aeppli, G; Shapiro, S M; Maletta, H; Birgeneau, R J; Chen, H S

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), Journal Name: J. Appl. Phys.; (United States) Vol. 55:6; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals &amp; Alloys-- Physical Properties
360603 -- Materials-- Properties
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
ALUMINIUM ALLOYS
AMORPHOUS STATE
BORON ALLOYS
CHALCOGENIDES
COHERENT SCATTERING
CORRELATIONS
DIFFRACTION
EUROPIUM COMPOUNDS
EUROPIUM SULFIDES
FERROMAGNETISM
IRON ALLOYS
MAGNETISM
MANGANESE ALLOYS
NEUTRON DIFFRACTION
ORDER PARAMETERS
PHASE TRANSFORMATIONS
PHOSPHORUS COMPOUNDS
RARE EARTH COMPOUNDS
SCATTERING
SPIN GLASS STATE
STRONTIUM COMPOUNDS
STRONTIUM SULFIDES
SULFIDES
SULFUR COMPOUNDS
TEMPERATURE DEPENDENCE
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE