Small-moment antiferromagnetic ordering in single-crystalline La2 Ni7

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Ribeiro, R. A.
Bud'ko, S. L.
Xiang, L.
Ryan, D. H.
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Iowa State University Digital Repository, Ames IA (United States)
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Physics and AstronomyAmes National Laboratory
Single crystals of La2Ni7 have been grown out of a binary La-Ni melt. Temperature-dependent, zero magnetic field, specific heat, electrical resistivity, and low field magnetization measurements indicate that there is a series of antiferromagnetic (AFM) phase transitions at T-1 = 61.0 +/- 0.2K, T-2 = 56.5 +/- 0.2K, and T-3 = 42.2 +/- 0.2K. The three specific heat anomalies found at these temperatures qualitatively have very small entropy changes associated with them, and the anisotropic M(H) data saturate at similar to 0.12 mu(B)/Ni; both observations strongly suggesting the AFM order is associated with very small, itinerant moments. Anisotropic H-parallel to c and H-perpendicular to c, rho(H) and M(H) isotherms as well as constant field rho(T) and M(T) sweeps manifest signatures of multiple phase lines and result in H-T phase diagrams that are clearly anisotropic. Analysis of M(T) and M(H) data allow for the identification of the two lower temperature magnetically ordered states as AFM ordered, with the moments aligned along the crystallographic c axis, and the higher temperature T-2 < T < T-1 state as having a finite ferromagnetic component. In addition, the metamagnetic transition at low temperatures, for H applied along the crystallographic c axis (H-parallel to c), appears to be a near classic example of a spin-flop transition, resulting in a field stabilized AFM state with the moments ordered perpendicular to the c axis. Although the small moment ordering and existence of multiple phase transitions in field and temperature, suggesting an energetic proximity of these states, could foretell a degree of pressure sensitivity, our measurements of R(T) for applied pressures up to 2.0 GPa indicate that there is very little pressure dependence of T-1, T-2, and T-3.
This article is published as Ribeiro, Raquel A., Sergey L. Bud'ko, Li Xiang, Dominic H. Ryan, and Paul C. Canfield. "Small-moment antiferromagnetic ordering in single-crystalline La 2 Ni 7." Physical Review B 105, no. 1 (2022): 014412. DOI: 10.1103/PhysRevB.105.014412. Copyright 2022 American Physical Society. DOE Contract Number(s): AC02-07CH11358; GBMF4411. Posted with permission.