Transport and magnetic properties of GdBaCo_{2}O_{5+x} single crystals: A cobalt oxide with square-lattice CoO_2 planes over a wide range of electron and hole doping

Abstract

Single crystals of the layered perovskite GdBaCo_{2}O_{5+x} (GBCO) have been grown by the floating-zone method, and their transport, magnetic, and structural properties have been studied in detail over a wide range of oxygen contents. The obtained data are used to establish a rich phase diagram centered at the "parent'' compound GdBaCo_{2}O_{5.5} -- an insulator with Co ions in the 3+ state. An attractive feature of GBCO is that it allows a precise and continuous doping of CoO_{2} planes with either electrons or holes, spanning a wide range from the charge-ordered insulator at 50% electron doping (x=0) to the undoped band insulator (x=0.5), and further towards the heavily hole-doped metallic state. This continuous doping is clearly manifested in the behavior of thermoelectric power which exhibits a spectacular divergence with approaching x=0.5, where it reaches large absolute values and abruptly changes its sign. At low temperatures, the homogeneous distribution of doped carriers in GBCO becomes unstable, and both the magnetic and transport properties point to an intriguing nanoscopic phase separation. We also find that throughout the composition range the magnetic behavior in GBCO is governed by a delicate balance between ferromagnetic (FM) and antiferromagnetic (AF) interactions, which can be easily affected by temperature, doping, or magnetic field, bringing about FM-AF transitions and a giant magnetoresistance (MR) phenomenon. An exceptionally strong uniaxial anisotropy of the Co spins, which dramatically simplifies the possible spin arrangements, together with the possibility of continuous ambipolar doping turn GBCO into a model system for studying the competing magnetic interactions, nanoscopic phase separation and accompanying magnetoresistance phenomena.

arXiv comment31 pages, 32 figures, submitted to Phys. Rev. B

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Cited by in corpus (27)

• Topotactic phase transformation of the brownmillerite SrCoO2.5 to the perovskite SrCoO3-δ
• Origin of the large thermoelectric power in oxygen-variable RBaCo_{2}O_{5+x} (R=Gd, Nd)
• Electron-Hole Asymmetry in GdBaCo_{2}O_{5+x}: Evidence for Spin Blockade of Electron Transport in a Correlated Electron System
• Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho
• Magnetic and electronic Co states in layered cobaltate GdBaCo2O5.5-x
• Formation of magnetic glass in calcium doped YBaCo2O5.5 cobaltites
• Electron transport and thermoelectric properties of layered perovskite LaBaCo2O5.5
• Large magnetothermal conductivity in GdBaCo_{2}O_{5+x} single crystals
• Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x
• Doping n-type carriers by La-substitution for Ba in YBa_2Cu_3O_y system
• First principles study of the spin state transitions in GdBaCo${}_2$O${}_{5.5}$
• Effect of Oxygen Content on Magnetic Properties of Layered Cobaltites PrBaCo2O5+δ
• Probing phase coexistence and stabilization of the spin-ordered ferrimagnetic state by Calcium addition in the YBa_{1-x}Ca_{x}Co_{2}O_{5.5} layered cobaltites using neutron diffraction
• Existence of the Co3+ Low Spin State in TbBaCo2O5.5
• Charge ordering transition in GdBaCo2O5: evidence of reentrant behavior
• Structure and Magnetism of HoBaCo2O5+delta Layered Cobaltites with 0.02<delta<0.22
• Enhancement of ferromagnetism by nickel doping in the 112 cobaltite EuBaCo2O5.50
• Magnetic and Electronic properties of Eu0.9Ca0.1BaCo2O5.5+? with the disparity of Oxygen Stoichiometry
• Prominent electron-hole asymmetry in thermoelectric transport of LaCoO${}_3$
• High temperature behavior of Sr-doped layered cobaltites Y(Ba1-xSrx)Co2O5.5: phase stability and structural properties
• Proof-of-concept thermoelectric oxygen sensor exploiting oxygen mobility of GdBaCo2O5+δ
• Carrier filtering effect for enhanced thermopower in a body-centered tetragonal ruthenate
• Electron doping induced magnetic glassy state in phase separated YBaCo${}_2$O${}_{5.5-\delta }$
• Magnetic glassy state at low spin state of Co3+ in EuBaCo2O5+δ (δ = 0.47) cobaltite
• Coupling of magnetism and transport properties to the lattice degrees of freedom in NdBaCo${}_2$O${}_{5+\delta }$ ($\delta \sim 0.65$)
• Anomalous Hall Resistivity of TbBaCo2O5.53 with Non-trivial Magnetic Structure
• Nanoscale ordered Layered-Segregation of Cobalt and Iron in the Perovskite SmFe0.5Co0.5O3