Nanometer-Thick Yttrium Iron Garnet Films with Perpendicular Anisotropy and Low Damping

Y3Fe5O12 (YIG) thin films having a thickness of several nanometers and showing both strong perpendicular magnetic anisotropy (PMA) and low magnetic damping are reported. The films are deposited by magnetron sputtering at room temperature first and then annealed in O-2 at high temperature. The substrates are Gd-3(Sc2Ga3)O-12, which share the same crystalline structure as YIG, but have a lattice constant slightly larger than that of YIG; the lattice mismatching gives rise to an out-of-plane compressive strain and PMA in the YIG films. The PMA is confirmed by vibrating sample magnetometer, magneto-optical Kerr effect, anomalous Hall effect, and angle-dependent ferromagnetic resonance (FMR) measurements. The damping of the films is analyzed through frequency-dependent FMR measurements. As an example, an 8-nm-thick YIG film shows an effective PMA field of about 2800 Oe, a nearly square hysteresis loop, and a damping constant of only 4.2 x 10(-4). As an illustration of possible applications of such films in spintronic devices, current-induced switching of the magnetization of the PMA YIG films is demonstrated by the use of YIG/Pt bilayered Hall bar devices.