Magnetic Field Dependence of the Small-Angle Neutron Scattering (SANS) in Amorphous DyCu and NdFe2

Author

Donna Marie Andrauskas, University of Rhode Island

Date of Award

1985

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics

First Advisor

Stanley Pickart

Abstract

Previous data on amorphous NdFe₂ have shown that it has some sort of phase transition at approximately 330 K. Previous magnetization studies on amorphous DyCu have shown that this alloy undergoes some sort of phase transition at approximately 17 K. Unusual field cooling and time relaxation effects were also observed in these measurements on Dycu below this temperature. these phase transitions and Both the exact the resultant nature of magnetic structures of these alloys are not yet fully understood. This study was undertaken to obtain additional information about them.

Small-angle neutron scattering data- on amorphous NdFe₂ were taken in zero field and in applied fields up to 18 kOe. In zero field, the lineshape of the scattering was Lorentzian above the transition temperature and became increasingly deviated from this form below this temperature. The spin correlation length showed a broad maximum near to, but lower than, the transition temperature and then decreased below this temperature. SANS data obtained with the applied field showed a sharp decrease in intensity with increasing field. The spin correlation length also decreased with increasing field.

The response of the SANS from amorphous DyCu to applied fields up to 15 kOe was examined. Application of the field caused a decrease in SANS intensity with increasing field and also caused a decrease in the correlation length which was obtained from the lineshapes which were Lorentzian to 6 A from the zero field value of c 13.5 a Time relaxation effects were observed in the field-cooled data.

The SANS measurements showed that amorphous Dycu and NdFe₂ do not have a magnetic phase transition to long-range ferromagnetism. .They indicated that these alloys undergo a transition to a state that has some features of a spin glass.

Recommended Citation

Andrauskas, Donna Marie, "Magnetic Field Dependence of the Small-Angle Neutron Scattering (SANS) in Amorphous DyCu and NdFe2" (1985). Open Access Master's Theses. Paper 1336.
https://digitalcommons.uri.edu/theses/1336