arXiv subjects

A. Douglass

Publications and source records attributed to A. Douglass.

3 recordsLinked to original sources

arXiv2006

Borderline magnetism in Sr4Ru3O10: Impact of dilute La and Ca doping on itinerant ferromagnetism and metamagnetism

An investigation of La and Ca doped Sr4Ru3O10, featuring a coexistence of interlayer ferromagnetism and intralayer metamagnetism, is presented. La doping readily changes magnetism between ferromagnetism and metamagnetism by tuning the density of states. It also results in different Curie temperatures for the c-axis and the basal plane, highlighting a rare spin-orbit coupling with the crystal field states. In contrast, Ca doping enhances the c-axis ferromagnetism and the magnetic anisotropy. La doping also induces a dimensional crossover in the interlayer transport whereas Ca doping exhibits a tunneling magnetoresistance and an extraordinary T3/2-dependence of the resisitivity. The drastic changes caused by the dilute doping demonstrate a rare borderline magnetism that is delicately linked to the interplay of the density of states and spin-orbit coupling.

cond-mat.str-el↗

arXiv2005

Itinerant Ferromagnetism and Metamagnetism in Cr Doped Perovskite Ruthenates

We report results of structural, magnetic and transport properties of single crystal CaRu1-xCrxO3 (0≤x≤0.36) and SrRu1-xCrxO3 (0≤x≤0.30). Cr substitution as low as x=0.08 drives CaRu1-xCrxO3 from the paramagnetic state to an itinerant ferromagnetic state with field-driven first-order metamagnetic transitions leading to a sizeable saturation moment (~0.4B/f.u.within the ab plane). The ferromagnetism occurs abruptly and reaches as high as TC=123 K for x=0.22. The Cr-driven ferromagnetism is highly anisotropic, suggesting an important role for spin-orbit coupling. Lattice constant and magnetic measurements strongly support the valence of the Cr as tetravalent (Cr4+, 3d2 configuration). Cr substitution for Ru in SrRuO3 (TC=165 K) enhances the itinerant ferromagnetism, with TC reaching 290 K for x=0.30, consistent with Cr-induced ferromagnetism in paramagnetic CaRuO3. Preliminary pressure-dependent magnetization of CaRu0.85Cr0.15O3 shows strong enhancement of the saturation magnetization (25% for P~0.7 GPa). All results indicate a coupling of Ru 4d and Cr 3d electrons that is unexpectedly favorable for itinerant ferromagnetism which often exists delicately in the ruthenates.

cond-mat.str-el↗

arXiv2005

Observation of oscillatory magnetoresistance periodic in 1/B and B in Ca3Ru2O7

We report magnetoresistance oscillations in high magnetic fields, B, up to 45 T and over a wide range of temperature in the Mott-like system Ca3Ru2O7. For B rotating within the ac-plane, slow and strong Shubnikov-de Haas (SdH) oscillations periodic in 1/B are observed for T≤1.5 K in the presence of metamagnetism. These oscillations are highly angular dependent and intimately correlated with the spin-polarization of the ferromagnetic state. For B||[110], oscillations are also observed but periodic in B (rather than 1/B) which persist up to 15 K. While the SdH oscillations are a manifestation of the presence of small Fermi surface (FS) pockets in the Mott-like system, the B-periodic oscillations, an exotic quantum phenomenon, may be a result of anomalous coupling of the magnetic field to the t2g-orbitals that makes the extremal cross-section of the FS field-dependent.

cond-mat.str-el↗