FexMn1-x alloy phases strained in thin films: Depth-dependent investigation of FexMn1-x/Ir(001) multilayers by x-ray diffraction

X-ray-diffraction measurements have been performed on FexMn1-x(001) thin fi lms strained in Ir/FexMn1-x/lr(001) sandwiches and in [FexMn1-x/Ir](20) sup erlattices with x = 0.7 and x = 0.9. These concentrations were chosen with regard to the magnetic properties of the alloys. Superconducting quantum in terference device measurements showed a ferromagnetic state above x approxi mate to 0.75 and an antiferromagnetic or a nonmagnetic one below. The sampl es have been investigated by using the atomic contrast available through an omalous diffraction and by recording reciprocal space maps (RSM). The (111) RSM, sensitive to both in-plane and out-of-plane parameters, has been stud ied as a function of the grazing incidence angle. It has revealed that the [Fe0.9Mn0.1/Ir](20) superlattice has a complex structure with two phases st acked along the growth axis whose origin stems from the existence of the tw o cubic structures (bcc and fee) of the bulk alloys. In each case, we have shown that the FexMn1-x alloys are strained in a bet structure. This tetrag onalization allows us to investigate the magnetic properties throughout a c ontinuous transformation from a bcc phase (c/a = 1) to a fcc one (c/a = roo t 2). Together with x-ray resonant magnetic reflectivity measurements, our results show that the tetragonalization plays a dominant role on the magnet ic state observed for the investigated samples. For c/a in the range 1.2-1. 3, the Fe atoms are found to be in a ferromagnetic low-spin state. [S0163-1 829(99)04233-2].