Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme

TT 30.16: Poster

Thursday, March 11, 2004, 14:30–19:00, Poster A

Structure, Magnetism and Transport in Titanates — •H. Roth, N. Schittner, A. Elfilali, K. Kordonis, M. Cwik, A. Komarek, M. Reuther, R. Müller, T. Lorenz, M. Braden und A. Freimuth — II. Physikalisches Institut, Universität zu Köln, Zülpicher str. 77, 50939 Köln

The RTiO₃ compounds (R = Rare Earth) are typical Mott-insulators with ferro- or antiferromagnetic order depending on the radius of the R³⁺-ion. These Mott-insulators can be driven to a metal by hole doping. We have prepared single crystals of the systems La_1−xSr_xTiO₃, LaTiO_3+δ and Y_1−xCa_xTiO₃ and studied the magnetization and resistivity. The resistivity of La_1−xSr_xTiO₃ with 0.07 < x ≤ 0.2 show a T² behaviour over an unusually large temperature range up to 300 K. In contrast to La_1−xSr_xTiO₃, where the transition from antiferromagnetic to paramagnetic behaviour occurs around a hole concentration of 6 %/Ti, the antiferromagnetic order in LaTiO_3+δ is stable up to δ = 0.1, which formally corresponds to a hole concentration of 20 %/Ti. Both, oxygen- as well as Sr-doping causes a systematic decrease of the unusual orthorhombic splitting observed in the pure LaTiO₃. YTiO₃, the other end compound of the RTiO₃ series, is a ferromagnet with a magnetic moment of 0.9   µ_B. In Y_1−xCa_xTiO₃ the ferromagnetic order is strongly suppressed with increasing x and we find some indication for a sign change of the effective magnetic coupling, which could lead to a canted ferromagnetic ground state for 0.1<x<0.4. gefördert von der DFG durch den SFB 608