Critical phenomena and exchange interactions of an amorphous ferromagnet: gadolinium--gold. [80 Gd--20 Au]

Technical Report · Thu Jul 01 04:00:00 EDT 1976

DOI:https://doi.org/10.2172/7327038· OSTI ID:7327038

Poon, S. J.; Durand, J.

Magnetization was measured between 4 and 290/sup 0/K in fields up to 70 kOe on liquid-quenched Gd/sub 80/Au/sub 20/ amorphous alloys. The Curie temperature and critical exponents ..beta.., ..gamma.. and delta are found to be 149.45/sup 0/K, 0.439, 1.294 and 3.948 respectively. These values are compared with the Heisenberg and molecular field values. The data are fitted to an equation of state previously derived for second order phase transition in fluid systems. The results illustrate clearly a second order phase transition in the amorphous state. A discussion in terms of the Heisenberg model is presented. The effective magnetic moment in the paramagnetic state has a value of 9.37 ..mu../sub B/ per gadolinium atom. The saturation moment extrapolated to 0/sup 0/K is 7.0 ..mu../sub B/ per gadolinium atom. The low temperature saturation magnetization observes the T/sup /sup 3///sub 2// law from 0.13 T/sub c/ to 0.80 T/sub c/. The effective exchange integrals J/sub n/ determined from the Rushbrooke--Wood formula and spin-wave theory are found to be 2.28 and 1.34/sup 0/K respectively. The differences in J/sub n/ and that between the effective moment and saturation moment are attributed to the nearest-neighbor antiferromagnetic couplings below T/sub c/. Possible effects of structural disorder on the magnetic properties of Gd in the amorphous state are discussed. (auth)

• Research Organization: California Inst. of Tech., Pasadena (USA). W.M. Keck Lab. of Engineering Materials
• OSTI ID: 7327038
• Report Number(s): CALT-822-85
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ALLOYS
AMORPHOUS STATE
CURIE POINT
EQUATIONS
EQUATIONS OF STATE
EXCHANGE INTERACTIONS
GADOLINIUM ALLOYS
GADOLINIUM BASE ALLOYS
GOLD ALLOYS
INTERACTIONS
LOW TEMPERATURE
MAGNETIC MOMENTS
MAGNETIC PROPERTIES
MAGNETIZATION
MEDIUM TEMPERATURE
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE