Pressure-induced insulating state in (La,Sr)CoO3

We have investigated the effect of pressure on the electronic, magnetic, and structural properties on a single crystal of conducting, ferromagnet (TC=157 K) La0.82Sr0.18CoO3 located near the boundary of the metal-insulator transition. Contrary to the results reported on related systems, we find a transition from the conducting state to an insulating state and a decrease of TC with increasing pressure while the lattice structure remains unchanged. We show that this unusual behavior is driven by a gradual change of the spin state of Co3+ ions from magnetic intermediate-spin (t2g5eg1;S=1) to a nonmagnetic low-spin (t2g6eg0;S=0) state.

[1]  M. Kriener,et al.  Structure, magnetization, and resistivity of La 1 − x M x CoO 3 ( M = Ca , Sr, and Ba) , 2004, cond-mat/0401400.

[2]  Mahmud Tareq Hassan Khan,et al.  Observation of low, intermediate, and high spin states in GdBaCo 2 O 5.45 , 2002 .

[3]  A. Maignan,et al.  Magnetoresistance in the oxygen deficient LnBaCo2O5.4 (Ln=Eu, Gd) phases , 1997 .

[4]  A. Kityk,et al.  Infinite Lifshitz point in incommensurate type-I dielectrics , 1999 .

[5]  E. Pugh,et al.  Superconductivity on the border of itinerant-electron ferromagnetism in UGe2 , 2000, Nature.

[6]  G. Sawatzky,et al.  Intermediate-spin state and properties of LaCoO3. , 1996, Physical review. B, Condensed matter.

[7]  Ziqin,et al.  Random successive growth model for pattern formation. , 1995, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[8]  R. D. Shannon,et al.  Effective ionic radii in oxides and fluorides , 1969 .

[9]  Y. Morii,et al.  Simultaneous metal-insulator and spin-state transitions in Pr 0.5 Ca 0.5 CoO 3 , 2002 .

[10]  C. Leighton,et al.  Glassy ferromagnetism and magnetic phase separation in La1-xSrxCoO3 , 2003 .

[11]  H. Wilhelm,et al.  Transport Properties of Heavy Fermion Compounds , 1997, cond-mat/9711089.

[12]  M. Itoh,et al.  Spin-Glass Behavior and Magnetic Phase Diagram of La1-xSrxCoO3 ( 0 ≤x ≤0.5) Studied by Magnetization Measurements , 1994 .

[13]  Y. Takeda,et al.  Electronic structure and temperature-induced paramagnetism , 1997 .

[14]  N. Mōri,et al.  Pressure Dependence of the 100 K Spin-State Transition in LaCoO3. , 1997 .

[15]  Y. Tokura,et al.  Thermally induced insulator-metal transition in LaCoO 3 : A view based on the Mott transition , 1998 .

[16]  J. Goodenough,et al.  Structural details and magnetic order of La 1-x Sr x CoO 3 (x<=0.3) , 1999 .

[17]  Masatoshi Imada,et al.  Metal-insulator transitions , 1998 .

[18]  J. Sarrao,et al.  Dynamical disorder of spin-induced Jahn-Teller orbitals with the insulator-metal transition in cobaltites. , 2003, Physical review letters.

[19]  T. Lorenz,et al.  Evidence for a low-spin to intermediate-spin state transition in LaCoO 3 , 2002, cond-mat/0205479.

[20]  M. Takano,et al.  Pressure-induced transition from a charge-disproportionated antiferromagnetic state to a charge-uniform ferromagnetic state in Sr(2/3)La(1/3)FeO3. , 2002, Physical review letters.