Superconductivity and Quantum Critical Behavior in Cr_{100-z}Os_z

The magnetic phase diagrams of Cr alloys with group-8 metals, such as Re and Ru, show interesting properties. These include quantum critical and superconducting behavior. In order to extend these investigations this paper reports on the physical properties and the magnetic phase diagram of the $Cr_{100-z}Os_{z}$ system, investigated in a concentration range of 2 ≤ z ≤ 30.6. Structural analysis indicate that samples with z<22 have a bcc structure, while those with z>22 include a cubic A15-type structure. Transport and magnetic property measurements indicate that the antiferromagnetic phase disappears at z ≈ 14 and that samples with concentrations z ≥ 12.2 show superconducting behavior. The magnetic phase diagram of $Cr_{100-z}Os_{z}$ is constructed from the Néel and superconducting transition temperatures obtained from various measurements. The commensurate spin-density-wave to paramagnetic phase line decreases sharply for z>4. Fitting parameters of a power law fit to the commensurate spin-density-wave to paramagnetic phase line indicate possible quantum critical behavior. Present results suggest that this phase line terminates in a superconducting dome near a magnetic quantum critical point, similar to that observed in certain heavy fermion systems, but not previously reported for other Cr alloys.