Magnetic and Electronic Quantum Criticality in YbRh2Si2

• Published in: Journal of low temperature physics 2010-10, Vol.161 (1-2), p.67-82
• Main Authors: Friedemann, S., Westerkamp, T., Brando, M., Oeschler, N., Gegenwart, P., Krellner, C., Geibel, C., MaQuilon, S., Fisk, Z., Steglich, F., Wirth, S.
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Breakdown; Characterization and Evaluation of Materials; Condensed Matter Physics; Instability; Magnetic Materials; Magnetic permeability; Magnetism; Magnetoresistivity; Phase diagrams; Physics; Physics and Astronomy; Rhodium; Stability
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-010-0201-8

The unconventional nature of the quantum criticality in YbRh 2 Si 2 is highlighted on the basis of magnetoresistivity and susceptibility measurements. Results obtained under chemical pressure realized by isoelectronic substitution on the rhodium site are presented. These results illustrate the position of the T ⋆ -line associated with a breakdown of the Kondo effect near the antiferromagnetic instability in the low-temperature phase diagram. Whereas at zero temperature the Kondo breakdown and the antiferromagnetic quantum critical point coincide in the proximity of the stoichiometric compound, they are seen to be detached under chemical pressure: For positive chemical pressure the magnetically ordered phase extends beyond the T ⋆ ( B )-line. For sufficiently high negative pressure the T ⋆ ( B )-line is separated from the magnetically ordered phase. From our detailed analysis we infer that the coincidence is retained at small iridium concentrations, i.e. , at small negative chemical pressure. We outline further measurements which may help to clarify the detailed behavior of the two instabilities.