Magnetic Behavior of Complex Oxide Magnetic Tunnel Junctions
ORAL
Abstract
Half metallic manganese oxides have the potential of producing a large tunneling magnetoresistance (TMR) due to their high spin-polarization. To explore their applicability we investigated magnetic tunnel junctions (MTJs) with ferromagnetic La$_{0.7}$Ca$_{0.3}$MnO$_3$(LCMO) electrodes and an insulating PrBa$_2$Cu$_3$O$_7$(PBCO) barrier. In these MTJs, with temperature, the TMR peaks rather than increasing with decreasing T [1]. Our Polarized Neutron Reflectivity studies reveal differences in the magnetization, reversal behavior, and anisotropy, between the bottom and top LCMO layers. As was observed in the YBa$_2$Cu$_3$O$_7$(YBCO)/LCMO system[2,3], with X-Ray Magnetic Circular Dichoism we have found a non-zero net moment on the Cu of PBCO at low temperature, originating at the interface. Unlike for YBCO, the Cu moment does not persist up to T$_C$ of LCMO. These combined results provide a possible origin of the anomalous TMR behavior.\\[0pt] [1] Z. Sefrioui et al., Appl. Phys. Lett. 88, 022512 (2006) [2] J. Chakhalian et al., Nature Phys. 2, 244 (2006); Science 318, 1114 (2007) [3] C. Visani et al., Phys. Rev. B 84, 060405(R) (2011)
*Work supported by US Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract Nos. DE-AC02-06CH11357, DE-AC52-06NA25396 and the Spanish MICINN.
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