Degree of perfection of the ⟨111⟩ texture and the hysteresis of magnetoresistance in MnIr-based top spin valves

Dc magnetron sputtering was used to prepare spin valves based on an Mn75Ir25 antiferromagnet with a composite free layer Ni80Fe20/Co90Fe10 and different thicknesses of the magnetic and nonmagnetic layers. Investigations of the microstructure and texture have been performed using X-ray diffraction and transmission electron microscopy. Field dependences of the magnetoresistance were measured for samples with a different degree of perfection of the axial texture < 111 >: from sharp (with an orientation spread angle of 3.3 degrees) to strongly smeared (with an orientation spread angle of 19.3 degrees). It has been found that the width of the low-field loop of the magnetoresistance hysteresis increases monotonically with a decrease in the texture strength from sample to sample. The results are interpreted with allowance for the dependence of the hysteresis-loop width on the mutual orientation of the external magnetic field and easy axes of individual crystallites of the textured film.