Structure and magnetism in CePt2+x

Neutron diffraction results for CePt2+x alloys with 0≤x≤1, combined with low resolution room temperature x-ray diffraction and electron microscopy, confirm that the alloys are single phase. The data can be fit for all x with nearly equal agreement factors by structural refinements in either the C15 (MgCu2) phase or the C15b (AuBe5) structure. Observation of small peaks in the diffraction pattern for CePt3 that are forbidden in C15 suggest that C15b is the correct structure for this composition (and possibly for the other alloy compositions); and application of Hamilton close-quote s test indicates that the C15b structure is preferred over the C15 to the 95% confidence level. Magnetic susceptibility and specific heat measurements indicate that the cerium is essentially localized and trivalent for all x. The antiferromagnetism observed for CePt2 may be absent in the alloys, which behave as typical nonmagnetic cerium heavy fermion compounds with Kondo temperature TK∼2K. copyright 1997 The American Physical Society