Abstract
We report on high-resolution dc-magnetization measurements on a high-quality single crystal of YbCoSi. was measured down to 0.05 K and in fields up to 3 T, with the magnetic field oriented along the crystallographic directions , , and of the tetragonal structure. In a small field T two antiferromagnetic (AFM) phase transitions have been detected at K and K, in the form of a sharp cusp and a sudden drop in . These signatures confirm that the phase transitions are second order at and first order at . The AFM order is completely suppressed by fields as high as , 1.88, and 2.35 T for , , and , respectively. At these fields, reaches its saturation values and , which match quite well those calculated for the ground state proposed in C. Klingner, C. Krellner, M. Brando, C. Geibel, and F. Steglich [New J. Phys. 13, 083024 (2011)] and which confirm the trivalent state of the Yb ions in YbCoSi. We have derived the - phase diagrams along the three crystallographic directions from isothermal and isofield measurements. Four AFM regions can be identified for parallel to and , which are separated by first- and second-order phase-transition lines, showing anisotropy in the basal plane. For parallel to only two AFM phases have been observed. The phase boundary , which separated the AFM phase from the paramagnetic one, can be well described by the empirical relation with close to 2.
- Received 13 July 2011
DOI:https://doi.org/10.1103/PhysRevB.84.224401
©2011 American Physical Society