Anomalous quantum criticality in an itinerant ferromagnet.
The dynamics of continuous phase transitions is governed by the dynamic scaling exponent relating the correlation length and correlation time. For transitions at finite temperature, thermodynamic critical properties are independent of the dynamic scaling exponent. In contrast, at quantum phase transitions where the transition temperature becomes zero, static and dynamic properties are inherently entangled by virtue of the uncertainty principle. Consequently, thermodynamic scaling equations explicitly contain the dynamic exponent. Here we report on thermodynamic measurements (as a function of temperature and magnetic field) for the itinerant ferromagnet Sr1-xCaxRuO3 where the transition temperature becomes zero for x=0.7. We find dynamic scaling of the magnetization and specific heat with highly unusual quantum critical dynamics. We observe a small dynamic scaling exponent of 1.76 strongly deviating from current models of ferromagnetic quantum criticality and likely being governed by strong disorder in conjunction with strong electron-electron coupling.
Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany.|Physikalisches Institut, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany.
C L
CL
Huang
Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany.
D
D
Fuchs
Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany.
M
M
Wissinger
Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany.
R
R
Schneider
Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany.
M C
MC
Ling
Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany.
M S
MS
Scheurer
Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany.|Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany.
J
J
Schmalian
Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany.|Physikalisches Institut, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany.
H V
HV
Löhneysen