Ultrathin CoPt-pinned current perpendicular to the plane spin valves

Abstract

The magnetics and magnetotransport of current perpendicular to the plane (CPP) giant magnetoresistive (GMR) spin valves utilizing thin CoPt hard magnet pinning layers on Cr seed layers are investigated. 50-Å-thick CoPt18 films grown on >20Å Cr seed layers exhibit a coercivity of ∼1.5kOe and a resistivity of 31μΩcm. The low critical thickness of the CoPt hard magnet compared to IrMn or PtMn antiferromagnets makes it an attractive pinning material for small gap CPP sensors required for high magnetic recording densities. Furthermore, CoPt∕Ru∕CoFe trilayers exhibit strong antiparallel coupling and the low CoPt resistivity minimizes parasitic resistance yielding a higher magnetoresistance. Moreover, free layers with coercivities and coupling fields in a range of 5–10 Oe have been measured, demonstrating that free layer softness does not suffer from the proximity to the CoPt hard magnet due to the relatively thick spacer layers compatible with CPP GMR sensors. In particular we deposited CoPt18 pinned antiferromagnetically coupled spin with a variety of reference layers. The films were patterned into pillars with diameters ranging from 50 to 200 nm by using a combination of electron beam lithography and ion milling. The devices exhibit a magnetoresistance up to 3.6% and a resistance area product of only 20mΩμm2.