Extrinsic Curie temperature and spin reorientation changes in Nd{sub 2}Fe{sub 14}B/{alpha}-Fe nanocomposites

Technical Report · Fri May 01 04:00:00 EDT 1998

DOI:https://doi.org/10.2172/672116· OSTI ID:672116

Lewis, L H ^[1]; Panchanathan, V ^[2]

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1. Brookhaven National Lab., Upton, NY (United States)
2. Magnequench International, Inc., Anderson, IN (United States)

The Curie temperatures and spin reorientation temperatures of a series of four melt-spun nanocomposite materials comprised of Nd{sub 2}Fe{sub 1}4B and varying amounts of {alpha}-Fe were measured using independent techniques. The phase constitution and grain size was assessed with synchrotron x-ray diffraction; the Curie temperatures were measured by differential thermal analysis (DTA) and dc SQUID magnetometry in the temperature range 375 K {le} T {le} 800 K, whereas the spin reorientation transition temperature was determined from ac susceptibility measurements taken in the range 10 K {le} T {le} 300 K. The Curie temperature increases with increasing excess iron content, resulting in a 18 {degree} enhancement over the Curie temperature of pure Nd{sub 2}Fe{sub 14}B for 27 wt% excess {alpha}-Fe. The spin reorientation temperatures are depressed from the single-crystal value by an average of 10 degrees. Both anomalous effects are attributed to intergranular exchange coupling present in the alloys, although the effects of uncompensated stress between the constituent phases cannot be ruled out The experimental results suggest that while the Curie temperature of the Nd{sub 2}Fe{sub 14}B phase may be extrinsically enhanced significantly beyond the bulk value, possibly extending the range of applications of this compound, the anisotropy may be simultaneously lowered, impeding the attainment of high coercivities in these alloys.

• Research Organization: Brookhaven National Lab., Neutral Particle Beam Div., Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 672116
• Report Number(s): BNL--65211; CONF-980802--; ON: DE98005715; BR: KC020205
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON ALLOYS
COMPOSITE MATERIALS
CURIE POINT
EXPERIMENTAL DATA
IRON
IRON ALLOYS
MAGNETIC PROPERTIES
NEODYMIUM ALLOYS
SPIN ORIENTATION
STOICHIOMETRY