Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 22: CE: Spin Systems and Itinerant Magnets
TT 22.9: Talk
Wednesday, March 24, 2010, 11:45–12:00, H21
Quantum Phase Transitions in Single-Crystal Mn1−xFexSi and Mn1−xCoxSi: I. Crystal Growth, Magnetization and Specific Heat — •Andreas Bauer, Andreas Neubauer, Christian Franz, and Christian Pfleiderer — Physik Department E21, Technische Universität München, D-85747 Garching, Germany
The helimagnetic transition in MnSi is suppressed under substitutional doping with Fe and Co on the Mn site. We report a comprehensive study of the magnetization and specific heat of single-crystal Mn1−xFexSi and Mn1−xCoxSi. With increasing concentration x the magnetic phase diagram remains essentially unchanged, exhibiting three phases (helical order, conical order and the Skyrmion lattice phase). In addition an extended cross-over regime exists between the paramagnetic and the helimagnetic state. When suppressing the magnetic modulations in an applied magnetic field, it is possible to infer the evolution of the underlying weakly ferromagnetic state as a function of x. In contrast to the pressure depencence of pure MnSi, which shows a first order quantum phase transition, we observe strong evidence for ferromagnetic quantum criticality.