Spin correlations and reentrant spin-glass behavior in amorphous Fe-Mn alloys. II. Dynamics

Journal Article · Thu Mar 01 04:00:00 EST 1984 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.29.2589· OSTI ID:6827516

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

Inelastic-neutron-scattering measurements have been performed on amorphous (Fe/sub 1-x/Mn/sub x/)/sub 75/P/sub 16/B/sub 6/Al/sub 3/ alloys for several concentrations x bracketing the spin-glass--ferromagnetic multicritical point found from magnetization measurements. For x = 0.35, the alloy is nonferromagnetic, and the inelastic spectra are dominated at all temperatures by a resolution-limited quasielastic peak. We find no evidence for propagating modes of any kind. In a 10-kG applied field, the central peak is substantially reduced, and dispersionless sidebands, centered at the Larmor precession frequency, appear. Three samples (x = 0.30, 0.25, and 0.20) on the ferromagnetic side of the phase diagram have also been studied. Spectra were collected for one of these (x = 0.25) above its Curie point. These data are consistent with ordinary spin diffusion. For all three samples, resolvable spin-wave peaks exist at temperatures below the Curie points but above the spin-glass transitions established in bulk measurements. As the temperature is reduced, the spin-wave stiffness first increases, as in normal ferromagnets, and then decreases. At the lowest temperatures, resolvable spin-wave peaks are absent, and the spectra are dominated by a resolution-limited (<30 ..mu..eV full width at half maximum) quasielastic peak. For the most iron-rich material (x = 0.20), true inelastic scattering coexists with the central peak, even at 5 K. This inelastic scattering broadens and decreases in intensity with increasing momentum transfer Q, in a manner consistent with simple spin-wave theory. The central-peak intensity decays according to a power law Q/sup -alpha/, with ..cap alpha..> or approx. =2.

• Research Organization: Brookhaven National Laboratory, Upton, New York 11973 and AT and T Bell Laboratories, Murray Hill, New Jersey 07974
• OSTI ID: 6827516
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 29:5; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals &amp; Alloys-- Physical Properties
ALLOYS
ALUMINIUM ALLOYS
ANGULAR MOMENTUM
BORON ALLOYS
COHERENT SCATTERING
DIFFRACTION
FERROMAGNETIC MATERIALS
INELASTIC SCATTERING
IRON ALLOYS
MAGNETIC MATERIALS
MANGANESE ALLOYS
MATERIALS
NEUTRON DIFFRACTION
PARTICLE PROPERTIES
PHASE TRANSFORMATIONS
QUANTITY RATIO
SCATTERING
SPIN
SPIN GLASS STATE