Temperature-dependent magnetic transitions in CoCrPt-Ru-CoCrPt synthetic ferrimagnets

Abstract

The magnetic orientations and switching fields of a CoCrPt-Ru-CoCrPt synthetic ferrimagnet with perpendicular magnetic anisotropy have been studied in the temperature range from 2 K to 300 K. It was found that two sets of magnetic transitions occur in the CoCrPt-Ru-CoCrPt ferrimagnet across this temperature range. The first set exhibits three magnetic transitions in the 50 K–370 K range, whereas the second involves only two transitions in the 2 K and 50 K range. The observed magnetic hysteresis curves of the synthetic ferrimagnet are explained using the energy diagram technique framework pioneered by Koplak et al. [1] which accurately describes the competition between interlayer exchange coupling energy, Zeeman energy, and anisotropy energy in the system. In this work we expand the framework to include synthetic ferrimagnets (SFMs) comprising higher perpendicular magnetic anisotropy materials and large (4X) interlayer exchange coupling energies which are promising for the development of ultrafast (ps) magnetic switching free layers in MTJ structures. Furthermore, we apply the analysis to predict SFM magnetic hysteresis curves in a temperature regime that includes temperature extrema that a synthetic ferrimagnet would be expected to reliably operate at, were it to be utilized as a free layer in a memory or sensor spintronic device.