Oscillations of magnetoresistance and anisotropic magnetoresistance in Tb/Cr/Fe structures

Sputtered Tb/Cr/Fe structures with a Cr layer (tCr) thickness ranging from 0 to 4 nm were prepared. The coercivity (Hc) of Tb/Cr (tCr)/Fe films with tCr ≥ 1 nm is consistent with that of the corresponding Cr(tCr)/Fe films. At the same time, the addition of the Tb layer results in a large saturation magnetization field (Hs) and even oscillatory relations of Hs on tCr, which might indicate an oscillatory indirect exchange coupling mediated by the spin polarization of the spacer Cr layer. Consistent oscillations are observed in anisotropic magnetoresistance (AMR) originating in spin–orbit coupling and magnetoresistance (MR) associated with interlayer exchange coupling as tCr in Tb/Cr/Fe films increases. The oscillatory MR demonstrates antiferromagnetic coupling, which also implies that it is not ordinary MR, although it is of the same magnitude as a result of the nonsharp interfaces. The value of the antiferromagnetic exchange coupling J as a function of tCr is estimated. Consistent oscillations with those in MR and AMR versus tCr are found, accompanied by a gradually flattened oscillation for films with tCr ≥ 2.5 nm resulting from weak coupling as the thick spacer Cr layer. Compared with the curves of MR, AMR, and J versus tCr, the opposite oscillations observed in the curve of Hc/Hs versus tCr further confirm the oscillatory interlayer exchange coupling in the studied structure, which provides theoretical basis for the adjustment of magnetic properties in spintronics by rare earth elements.