Design of solid solutions with perovskite and K 2 NiF 4 structures as substrate with tunable lattice parameters for HTSC and CMR epitaxy

Abstract

Suitability of various materials with the perovskite and K<SUB>2</SUB>NiF<SUB>4</SUB> structures as substrates for the epitaxy of high temperature superconductors (HTSC) and manganite perovskites with colossal magneto resistance (CMR) is studied. In particular, the analysis concentrates on solid solutions in LaGaO<SUB>3</SUB>-NdGaO<SUB>3</SUB> and SrLaGaO<SUB>4</SUB>-SrLaAlO<SUB>4</SUB> systems. The aim of the present investigation is to test the possibility of obtaining LaGaO<SUB>3</SUB>-NdGaO<SUB>3</SUB> solid solutions with cubic structure. Single crystal growth of LaGaO<SUB>3</SUB>-NdGaO<SUB>3</SUB> solid solutions in a selected NdGaO<SUB>3</SUB> concentration range has been investigated. It allows us to estimate the segregation coefficient for Nd in La<SUB>1-x</SUB>Nd<SUB>x</SUB>GaO<SUB>3</SUB>. Unit-cell parameters as a function of composition have been determined. Single crystal growth of SrLaGaO<SUB>4</SUB>-SrLaAlO<SUB>4</SUB> solid solutions has also been investigated. The optimum starting melt composition, the segregation coefficients for Ga in SrLaAlO<SUB>4</SUB> and Al in SrLaGaO<SUB>4</SUB> as well as the unit-cell parameters as a function of composition have been determined. Both LaGaO<SUB>3</SUB>-NdGaO<SUB>3</SUB> and SrLaGaO<SUB>4</SUB>-SrLaAlO<SUB>4</SUB> solid solutions are suitable substrate materials for HTSC and CMR perovskite epitaxy. Since their lattice parameters can smoothly be adjusted to those of deposited layers, the presented solid solutions are attractive substrate materials with tunable lattice parameters.