Magnetism of the tensile-strain-induced tetragonal state of SrRuO${}_{3}$ films

Magnetism of the tensile-strain-induced tetragonal state of SrRuO $_{3}$ films

A. Herklotz, M. Kataja, K. Nenkov, M. D. Biegalski, H.-M. Christen, C. Deneke, L. Schultz, and K. Dörr

Phys. Rev. B 88, 144412 – Published 14 October 2013

Abstract

SrRuO $_{3}$ films have been grown in the tetragonal, structurally single-domain state under 1% of biaxial tensile strain. The angular dependencies of the magnetization and the magnetoresistance reveal an upright orientation of the tetragonal unit cell and biaxial magnetic in-plane anisotropy with 110 $_{t}$ easy axes. Reversible biaxial strain from piezoelectric Pb(Mg $_{1 / 3}$ Nb $_{2 / 3}$ ) $_{0.72}$ Ti $_{0.28}$ O $_{3}$ (PMN-PT) substrates has been applied to probe the direct strain response of the magnetization and the electrical resistance. At 1% tensile strain, the Curie temperature ( $T_{C}$ ) and the ordered magnetic moment ( $m_{S}$ ) at low temperatures are found to substantially decrease with further growing tensile strain. This suggests a suppression of $m_{S}$ resulting from distortions of the RuO $_{6}$ octahedra, in line with reported density-functional calculations. Reversible strain has also been applied to a film under weak tensile strain revealing the opposite response, i.e., an enhancement of $T_{C}$ and $m_{S}$ with tensile strain. Structural and magnetic properties of SrRuO $_{3}$ films in several static strain states (compressive, weak and strong tensile strain) are compared.

Received 28 March 2013

DOI:https://doi.org/10.1103/PhysRevB.88.144412

Authors & Affiliations

A. Herklotz^1,2, M. Kataja², K. Nenkov², M. D. Biegalski³, H.-M. Christen³, C. Deneke⁴, L. Schultz², and K. Dörr¹

¹Martin Luther University Halle-Wittenberg, Institute for Physics, Von-Danckelmann-Platz 3, 06120 Halle, Germany
²IFW Dresden, Institute for Metallic Materials, Helmholtzstraße 20, 01069 Dresden, Germany
³ORNL, Center for Nanophase Materials Sciences, Bethel Valley Road, Oak Ridge, Tennessee 37831-6496, USA
⁴Laboratorio Nacional de Nanotecnologia, Rua Giuseppe Maximo Scolfaro, 10000 Campinas, Sao Paulo 13083-100, Brazil

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Vol. 88, Iss. 14 — 1 October 2013

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Images

Figure 1
Schemes of the investigated samples with the SrRuO $_{3}$ film thickness and the pseudocubic in-plane lattice parameter noted. The different substrates [STO (C) and PMN-PT (I, T1, T2)] and buffer layers Ba $_{x}$ Sr $_{1 - x}$ TiO $_{3}$ with $x = 0$ for (I) and $x = 0.75$ for (T1) were used to control the strain state from compressed (C) to nearly relaxed (I) to tensile (T).Reuse & Permissions
Figure 2
Reciprocal space maps around the {204} $_{s}$ lattice reflections of a sample of type T1. The reciprocal-lattice units are in terms of the PMN-PT pseudocubic bulk lattice parameter. The white crosses mark the position of a virtual cubic film with the pseudocubic lattice parameter of bulk SRO, $a =$ 3.923 Å.Reuse & Permissions
Figure 3
Angular dependent magnetoresistance of a C film (left side) and a T1 film (right side) at 130 K in a field of 7 T. In (a) and (c), the magnetic field was rotated within the (010) $_{s}$ plane and in (b) and (d) the field was rotated within the (100) $_{s}$ plane. The current was always perpendicular to the magnetic field. The solid red lines are fits of the expression in Eq. (2). The good agreement with the data for both current directions is a fingerprint of tetragonal symmetry in T films. The solid green and blue lines are fits to the expressions in (1) and (3), respectively, and are used to identify orthorhombic and monoclinic symmetry in C films, as explained in the text.Reuse & Permissions
Figure 4
Angular dependencies of magnetization in a T1 film with the field rotating about the 100 $_{s}$ axis (left) and in the film plane about the 001 $_{s}$ axis (right). $θ$ and $φ$ are the angles between the magnetic field and the 001 $_{s}$ and 100 $_{s}$ axis, respectively. The measurements were done at 10 K in a magnetic field of $μ_{0} H =$ 1.5 T. In the first measurement the data were recorded rotating back and forth to check for magnetic hysteresis as highlighted by the red arrows.Reuse & Permissions
Figure 5
Temperature dependence of the strain-induced $M$ change for the strain states with substrate fields of $E_{piezo} =$ 0 and 10 kV/cm, recorded for an I film (red) and for a T1 film (blue). The measurements were conducted in remanence after field cooling in $μ_{0} H =$ 0.1 T, in-plane along a direction 100 $_{s}$ . The dashed lines indicate the Curie temperatures of the films. The meaning of the colored areas are explained in the text. The inset illustrates the dependence of $T_{C}$ on the biaxial strain.Reuse & Permissions
Figure 6
(a) Temperature dependence of the electric resistance normalized to the room-temperature value for films in the C, I, and T2 states with the current direction along the 100 $_{s}$ axis. (b) Strain-induced change of the resistance between $E_{piezo} =$ 0 and 10 kV/cm for an I and a T2 film. The colored area indicates the contribution that is related to the ferromagnetic alignment as explained in the text. The dashed green line indicates the resistance change from the bare change of the geometry (length and cross section).Reuse & Permissions

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