Near Ferromagnetism in MnP-Type CoAs

We report the low temperature electrical and magnetic properties of single crystal CoAs. This material is isostructural with compounds like MnP, CrAs, and FeAs, which show intriguing superconducting and magnetic states as a function of temperature, magnetic field, and applied pressure. While there is no experimental evidence for magnetic ordering in CoAs, we have performed density functional theory calculations that favor a ferromagnetic ground state. Additionally, heat capacity and magnetization measurements suggest a ferromagnetic instability at low temperatures. De Haas-van Alphen oscillations observed at high fields support the calculated paramagnetic Fermi surface and give a measure of correlation strength. This talk will review the properties of CoAs in the light of other similar transition metal-pnictide binary materials.