Scanning tunneling spectroscopy under pulsed spin injection

An experimental technique combining cryogenic scanning tunneling spectroscopy (STS) and pulsed quasiparticle spin injection has been developed. The spin injection is intended to perturb a superconducting thin film from spin equilibrium, while the STS monitors its steady-state quasiparticle spectrum. A pulsed injection circuit was designed to minimize Joule heating while being both synchronized with and decoupled from the STS circuitry. A detailed description of the technique is presented, along with its application to spin-injection heterostructures comprising the half-metallic ferromagnet La0.7Ca0.3MnO3 and the high-Tc superconductor YBa2Cu3O7−δ.