SOME MAGNETIC STRUCTURE PROPERTIES OF TERBIUM AND OF TERBIUM-YTTRIUM ALLOYS
Neutron diffraction studies were made on single-crystal and polycrystalline specimens of terbium. Eariier magnetic and thermal measurements indicated a transformation to an ordered magnetic state at approximateiy 230 deg K, and a subsequent order-order transformation at approximately 220 deg K. The neutron measurements show that in the narrow antiferromagnetic region, the magnetic structure of terbium is a helical structure. The interlayer turn angle varies from 20.5 deg per layer at the Neel point to 18.5 deg per layer at the lower transition. At this lower temperature the structure transforms, in the absence of any external applied field, to a classical ferromagnetic structure in which the moments are in, or nearly in, the planes perpendicular to the hexagonal axis. At very low temperatures the magnetic moment per atom is very nearly 9.0 Bohr magnetons, the vaiue expected for the ordered tripositive ion. Neutron diffraction measurements were also made on a series of alloys of yttrium and terbium in order to study the influence of magnetic dilution on the magnetic properties of the rare-earth metals. Introduction of yttrium into terbium reduces the Neel temperature and broadens the range of existence of the helical phase. At 30 at.% yttrium and above, the spontaneous transformation to the ferromagnetic state is not observed, for zero applied field, even for temperatures as low as 4.2 deg K. As in pure terbium the interlayer turn angle omega of the helical structure in the alloys varies with temperature, but the slope of the omega vs temperature curve becomes smaller with increasing yttrium concentration. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-037703
- OSTI ID:
- 4630250
- Journal Information:
- Journal of Applied Physics (U.S.), Vol. Vol: 34; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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