Andreev reflection in ferrimagneticCoFe2O4spin filters

Abstract

We have performed point-contact spectroscopy measurements on a sample constituted by a metallic ferromagnetic oxide ͑SrRuO 3 ͒ bottom electrode and a tunnel ferrimagnetic ͑CoFe 2 O 4 ͒ barrier. Andreev reflection is observed across the tunnel barrier. From the comparison of Andreev reflection in SrRuO 3 and across the CoFe 2 O 4 barrier we infer that the ferrimagnetic barrier has a spin filter efficiency not larger than +13%. The observation of a moderate and positive spin filtering is discussed in the context of the microstructure of the barriers and symmetry-related spin-filtering effects.

The magnetization of epitaxial nanometric CoFe2O4(001) layers

“…We have verified that this is the case. 21 Finally, the shape of the out-of-plane magnetization curves ͑Fig. 1͑b͒͒ indicates that the maximum applied field ͑Ϸ48 kOe͒ is not sufficient to provide a high-field region where the ascending and descending branches of the loops coincide.…”

Spin-filtering efficiency of ferrimagnetic spinels CoFe2O4and NiFe2OCaffrey1, Fritsch2, Archer3 et al. 2013Phys. Rev. B

“…In addition, a good lattice match is of course required, otherwise translational symmetry is broken in the transverse plane and the complex band-structure argument breaks down. Here, the possibility to grow good quality films of 5,[7][8][9][10][11][12] So far, we have only discussed the spin character of the complex bands, whereas it is well known from the Fe/MgO/Fe system that the orbital character of the relevant bands can also have a crucial influence on the tunneling properties. The determination of orbital character of the complex bands in the inverse spinel ferrites CoFe 2 O 4 and NiFe 2 O 4 is complicated by the different symmetries of the specific cation configurations used in the calculations.…”

“…The reported values of P sf range from −44% to +26%. [7][8][9][10][11][12] Due to these large variations in experimental results (with both signs occurring for the spin-filtering efficiency), a conclusive picture of spin-filtering in spinel ferrites has not emerged, yet. As such, a first-principles investigation of the spin-filtering efficiency in these materials is highly desirable, in order to provide a reference for future experimental studies and to allow further optimization of the corresponding devices.…”

Mössbauer and Magnetic Properties of Coherently Mixed Magnetite-Cobalt Ferrite Grown by Infrared Pulsed-Laser Deposition

“…This wavelength is more unusual that the typical ultraviolet range. [5][6][7][8] In this work, we will show how Mössbauer spectroscopy is ideally suited to detect the mixture of magnetite and cobalt ferrite that is obtained under reducing conditions (i.e. high vacuum environment) on SrTiO3 : Nb (100) substrates.…”