J. W. Reiner

Transport and magnetization in the badly metallic itinerant ferromagnet SrRuO3

SrRuO3 is an itinerant ferromagnet with Tc 160 K and a bad metal in the limit of kF l D O.1/. While the magnetic properties of SrRuO3 in the paramagnetic phase, near the ferromagnetic phase transition and at low temperatures are normal and consistent with its being a strong itinerant ferromagnet, the transport properties (resistivity and magnetoresistance) sharply deviate from that of good metallic ferromagnets. We conjecture that the distinct transport behaviour of SrRuO3 is related to its being a bad metal in the kF l D O.1/ limit, and discuss the possible relevance of our results to the unusual transport properties of other bad metals such as high-temperature superconductors.

Lorentz transmission electron microscope study of ferromagnetic domain walls in SrRuO3: Statics, dynamics, and crystal structure correlation

The magnetic microstructure of SrRuO3 thin films is studied using Lorentz transmission electron microscopy (TEM). The zero-field-cooled magnetic stripe structure shows one-to-one correlation with the crystal domain structure and is used to identify the uniaxial magnetic anisotropy of these films, consistent with results on single domain films. The anisotropy is shown to be primarily magnetocrystalline in nature with the b axis as the easy axis. Lorentz TEM also yields quantitative information about the domain structure and domain wall resistivity, and allows for in situ observation of domain wall formation and dynamic response to an applied field.

Transport spin polarization in SrRuO3 measured through point-contact Andreev reflection

We report a study in which Andreev reflection using a Nb point contact is used to measure the transport spin polarization of the 4d itinerant ferromagnet SrRuO 3 in the ballistic limit of transport. The degree of transport spin polarization is comparable to that of the hole-doped rare-earth manganites. We conclude that the large transport spin polarization results mainly from a difference in the Fermi velocities between the majority- and minority-spin channels in this material.

Large magnetoresistance of single-crystal films of ferromagnetic SrRuO3

Measurements of single-crystal films of the itinerant ferromagnet SrRuO 3 show that: (a) the magnetoresistance (MR) near „ # &150 K is large (12% at H6 T), negative, and is described by a scaling function; (b) the (negative) anisotropic MR is large (20%); and (c) the domain walls are highly resistive (unit area resistance &10~15 ) m2). We believe that the MR properties of SrRuO 3 , which are strong relative to that of good metallic ferromagnets, are related to strong electron correlations. ( 1998 Elsevier Science B.V. All rights reserved.

Non-Fermi-Liquid Behavior of SrRuO{sub 3} : Evidence from Infrared Conductivity

The reflectivity of the itinerant ferromagnet SrRuO{sub 3} has been measured between 50 and 25thinsp000thinspthinspcm{sup {minus}1} at temperatures ranging from 40 to 300thinspthinspK, and used to obtain conductivity, scattering rate, and effective mass as a function of frequency and temperature. We find that at low temperatures the conductivity falls unusually slowly as a function of frequency (proportional to 1/{omega}{sup 1/2} ), and at high temperatures it even appears to increase as a function of frequency in the far-infrared limit. The data suggest that the charge dynamics of SrRuO{sub 3} are substantially different from those of Fermi-liquid metals. {copyright} {ital 1998} {ital The American Physical Society }

Suppression of the superconducting critical current of Nb in bilayers of Nb∕SrRuO3

In bilayers consisting of ferromagnetic and superconducting films, the ferromagnetic film in its domain state induces inhomogeneous distribution of magnetic fields in the superconducting film. When the ferromagnetic film has bubble magnetic domains in a labyrinth structure, it has been found that the pinning of the vortices increases; hence, the critical current of the superconducting film becomes larger. Here we study the effect of parallel ferromagnetic domain structure in Nb∕SrRuO3 on the critical current of Nb with current flowing perpendicularly to the domains and find that in this case the ferromagnetic domain structure decreases the critical current.

Domain-wall resistivity in SrRuO3: the influence of domain walls spacing

Abstract SrRuO 3 is an itinerant ferromagnet with a stripe domain structure. Here, we report how the resistivity due to the domain walls is affected when the density of the domain walls is decreased. We find that while the perpendicular resistivity is uniformly scaled down, the effect on the parallel resistivity seems to be temperature dependent. We discuss possible implications of these results.

Magnetic and Crystalline Microstructure of SrRuO 3 Thin Films

The relationship between the magnetic and crystalline microstructure of SrRu03 thin films is analyzed using transmission electron microscopy. Regions with a stripe magnetic domain structure in different orientations are observed in Lorentz imaging mode when the specimens are zero-field-cooled through the ferromagnetic transition temperature, T c ≈ 150K. The different orientations of the stripe regions correspond to different crystallographic domains as determined by electron diffraction and magnetic image contrast; all of the six possible orientations of the orthorhombic SrRuO 3 structure grown epitaxially on a SrTiO 3 cubic substrate are identified. The results show that the uniaxial anisotropy indicated for these multi(crystal)domain films is the same as that determined for single crystal films by bulk magnetization measurements, and is therefore primarily magnetocrystalline in nature.