Quantum Criticality and Heavy Fermion State in YbCo^sub 2^Zn^sub 20^ under Pressure and Magnetic Field

We studied an effect of pressure on the heavy fermion state of YbCo ... Zn ... under magnetic fields. The critical pressure P ... , where the electronic state changes from the heavy fermion state to the antiferromagnetic state, is estimated to be P ... ...1.8 GPa. The super-heavy fermion state in the P ... region is found to be strongly destroyed in magnetic fields for H ... . The field-induced quadrupolar phase, which is most likely realized only for H ... , is found to be robust even in the antiferromagnetic pressure region. (ProQuest: ... denotes formulae/symbols omitted.)