Manganite and YBCO spintronic devices

Manganite and YBa2Cu3O7 (YBCO) spintronic devices were created and tested. High tunneling magnetoresistance, a high resistance demagnetized state, and applied field angular dependences were found in manganite magnetic tunnel junctions. A switching signal and applied field angular dependence was seen YBCO/manganite spin diffusion measurement devices. Various unique YBCO/-manganite critical current suppression devices were measured and showed rather small gains.; La0.67Sr0.33MnO3/SrTiO3/La 0.67Sr0.33MnO3 (LSMO/STO/LSMO) magnetoresistive tunnel junctions were produced and tested. The junction resistance was measured as a function of temperature and magnetic field applied at various out-of-plane angles. A tunneling magnetoresistance (TMR) of 360% was found at 5K for the LSMO/STO/LSMO junctions. The TMR signal was present up to a temperature of 275K. Angular measurements showed increased switching fields with similar TMR values. An unusual high resistance state was found when the samples were demagnetized at low temperatures. Demagnetized samples showed higher TMR values and sharp switching in low magnetic field sweeps than when measured in standard high magnetic field sweeps. A TMR of 457% was found at 5K for the same LSMO/STO/LSMO junction quoted above. Differences in resistance between the demagnetized state and the lowest measured resistance state show that the TMR could be as large as 800% at 5K. Current-voltage (IV) measurements were taken and fit with a Simmons model to obtain the insulating barrier height and thickness. La0.67Ca0.33MnO3 (LCMO)/STO/LSMO junctions were also created and displayed anomalous temperature and angular dependence with varying TMR values.; LSMO/YBCO/LSMO spin diffusion measurement devices were created. Voltage was measured between a LSMO pad and a gold pad in contact with a thin YBCO layer subject to an injection current from a bottom LSMO layer. A voltage in such a configuration has been proposed to be generated by the diffusion of spin in the YBCO layer. Spin-like switching effects were seen. The voltage showed sharp switching between two states. An inversion in the switching between the two states was found based on the orientation of the sample in relation to the magnetic field. Effects were seen to differ from hall signals of a single LSMO layer. A spin diffusion length in YBCO at l00K was estimated be, delta s ≈ 0.1mum. A variety of YBCO/STO/LSMO and YBCO/STO/LaNiO3 (LNO) critical current suppression devices were created. The critical current of the YBCO was measured as a function of current injected from the LSMO/LNO layer. LSMO is a colossal magnetoresistive material (CMR) and is believed to have a highly spin polarized current (>80%). LNO is a unpolarized normal metal. The non-equilibrium state imposed by an injected polarized spin overpopulation in super-conducting YBCO has been proposed to have a larger critical current suppression than the unpolarized case. However, differences between the two injection cases are not found to be appreciable. Gains (-dI(C)/dI(Inj)) are found to be ≈1--3 at temperatures from 80K--20K for both injection scenarios. The largest gain for any device was ≈5, far below the critical temperature of YBCO.