Antiferromagnetic ground state in NpCoGe

Abstract: 

 

NpCoGe, the neptunium analog of the ferromagnetic superconductor UCoGe, has been investigated by dc magnetization, ac susceptibility, specific heat, electrical resistivity, Hall effect, 237Np Mossbauer spectroscopy, and local spin-density approximation (LSDA) calculations. NpCoGe exhibits an antiferromagnetic ground state with a Néel temperature TN ≈ 13 K and an average ordered magnetic moment μNp = 0.80μB. The magnetic phase diagram has been determined and shows that the antiferromagnetic structure is destroyed by the application of a magnetic field (3 T). The value of the isomer shift suggests a Np3+ charge state (configuration 5f 4). A high Sommerfeld coefficient value for NpCoGe (170 mJ mol−1 K−2) is inferred from specific heat. LSDA calculations indicate strong magnetic anisotropy and easy magnetization along the c axis. Mossbauer data and calculated exchange interactions support the possible occurrence of an elliptical spin-spiral structure in NpCoGe. The comparison with NpRhGe and uranium analogs suggests the leading role of 5f-d hybridization, the rather delocalized character of 5f electrons in NpCoGe, and the possible proximity of NpRuGe or NpFeGe to amagnetic quantum critical point.  
 

 

Authors
Authors: 
SHIK Alexander, GRIVEAU Jean-Christophe, ELOIRDI Rachel, CACIUFFO Roberto, GACZYNSKI Piotr, KHMELEVSKYI S., COLINEAU Eric
Publication Year
Publication Year: 
2014
Type

Type:

Appears in Collections
Appears in Collections: 
Institute for Transuranium Elements
Science Areas
Science Areas: 
JRC Institutes
ITU
Publisher
Publisher: 
AMER PHYSICAL SOC
ISSN
ISSN: 
1098-0121
Citation
Citation: 
PHYSICAL REVIEW B p. 115135 no. 11 vol. 89