Phase diagram of LaTiO
x
: from 2D layered ferroelectric insulator to 3D weak ferromagnetic semiconductor |
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Authors: | F Lichtenberg D Widmer J G Bednorz T Williams A Reller |
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Institution: | (1) IBM Research Division, Zurich Research Laboratory, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland;(2) Institute for Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland;(3) Present address: CSIRO Division of Materials Science and Technology, Locked Bag 33, 3168 Clayton, Victoria, Australia |
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Abstract: | LaTiO
x
compounds are structurally related to perovskites and there are two known phases. The first,x=3.50, is a 2D layered-type ferroelectric. The second,x=3.00, is a weak ferromagnet with a 3D orthorhombic distorted perovskite structure. 20 samples with varying oxygen stoichiometry between these end members were prepared by floating zone melting, and then characterized by means of X-ray powder diffraction, electron microscopy, thermogravimetric analysis, resistivity and magnetic measurement. A phase diagram is established which displays the following physical and structural properties. A structural phase boundary atx=3.20 separates a new series of 2D layered structures from the 3D orthorhombic one. The former series represents the first conducting titanium oxides with a 2D layered structure to be reported. Atx=3.10 a phase boundary exists between a metallic and a weak ferromagnetic state where the magnetic transition temperatureT
c
can be sensitively tuned by the oxygen stoichiometryx. Samples withT
c
between 100 K and 130 K exhibit a metal-semiconductor transition whereas samples with higherT
c
, up to 149 K, are semiconductors between room temperature and 4.2 K. |
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Keywords: | |
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