Oscillatory interlayer coupling and giant magnetoresistance in epitaxial Fe/Cr(211) and (100) superlattices

A epitaxial orientation of Fe/Cr superlattices—Fe/Cr(211) on MgO(110)—is grown by magnetron sputtering. Its structural and magnetic characterizations are presented and compared to those for Fe/Cr(100) superlattices grown simultaneously onto MgO(100) substrates. The epitaxial orientation of the Fe/Cr(211) superlattices is Fe/Cr[01¯1]∥MgO[001] and Fe/Cr[1¯11]∥MgO[11¯0], while that for Fe/Cr(100) is Fe/Cr[001]∥ MgO[011]. A uniaxial, in-plane surface anisotropy for the Fe/Cr(211) superlattices along the Fe[01¯1] of 0.06 erg/${\mathrm{cm}}^2$ is obtained from analysis of the magnetization hysteresis loops. Four oscillations in the antiferromagnetic interlayer coupling and giant magnetoresistance (GMR) are observed with a period of 18 Å for both orientations. The strength, oscillation period, and phase of the magnetic coupling are identical for the two orientations. The GMR values increase by a factor of ∼4 to 5 on cooling from room temperature to 4.2 K. At 4.2 K the maximum GMR value of the [Fe(14 Å)/Cr(8 Å)${]}_{50}$ superlattice is 70% for the (211) orientation and 150% for the (100) orientation.