Thickness and process optimization of planetary magnetron sputtered FeMnRhspin valves

Thickness dependence and process optimization of planetary magnetron sputte red FeMnRh-based spin valves (SV) have been investigated in terms of the in terrelationship between process conditions, microstructure, and magnetic pr operties. For the Cu spacer layer, sputtering at low power (0.5-1 kW) and l ow pressure (1-3 mT) give lower film resistivity. The Delta R/R reaches > 9 .0% for Cu thickness range of 18-22 Angstrom and drops as Cu thickness incr eases in spin valves of structure: Ta50/NiFe50/CoFe20/Cu(t)/CoFe22/FeMnRh80 /Ta50 Angstrom. From the pinned layer thickness (CoFe) dependence of H-ex, an interfacial anisotropy energy (J(k)=H(ex)M(s)t) is calculated to be 0.14 erg/cm(2) which is larger than the value reported for FeMnRh previously. B oth H-ex (400-480 Oe) and Delta R/R (7.3%-8.5%) were found to increase with FeMnRh sputtering pressure (3-15 mT) for Ta50/NiFe50/CoFe20/Cu26/CoFe22/Fe MnRh110/Ta50 Angstrom films. Two-step depositions (low and high sputtering pressure) of FeMnRh layer suggest that the higher H-ex is mainly attributed to the interfacial smoothness at the CoFe/FeMnRh interface rather than the effect of smaller grain size of FeMnRh layer. The blocking temperature (T- b) of these spin valves increases from 160 to 175 degrees C with increasing FeMnRh thickness from 80 up to 110 Angstrom, after which it decreases to 1 70 degrees C at 120 Angstrom. (C) 2000 American Institute of Physics. [S002 1-8979(00)87108-X].