Ferromagnetic hcp Fe in Fe/Re(001) multilayers

Until now, the hexagonal closed-packed (hcp) phase for bulk Fe, Fe multilay ers, or Fe alloys has always been associated with a paramagnetic state. We show evidence that hcp Fe can support a ferromagnetic moment in Fe/Re multi layers. The structure and magnetic properties of Fe/Re multilayers are stud ied using x-ray diffraction, energy dispersive x-ray analysis, magneto-opti cal Kerr-effect magnetometry, and x-ray magnetic circular dichroism. The Fe layer thickness tp, is maintained constant at 8 Angstrom, while 0 less tha n or equal to t(Re) less than or equal to 35 Angstrom. For t(Re) <8 Angstro m the multilayer has a body centered tetragonal (bct) structure with a perp endicular interplanar spacing that increases with increasing Re thickness. Beyond the t(Re) approximate to 9 Angstrom the structure transforms to hcp. Fe has a quite stable magnetic moment for all t(Re), before and beyond the structural phase transition.