Observation of the strain induced magnetic phase segregation in manganite thin films

Lorena Marín (1, 2, 3) , Luis A. Rodríguez (2, 1) , César Magén (2, 1) , Etienne Snoeck (4) , Rémi Arras (4) , Irene Lucas (1) , Luis Morellón (1, 4) , Pedro A. Algarabel (2, 3) , José M. de Teresa (2, 3) , M. Ricardo Ibarra (2, 1)

1 INA - Instituto de Nanociencia de Aragón [Saragoza, España]
2 Departamento de Física de la Materia Condensada
3 ICMA-CSIC - Instituto de Ciencia de Materiales de Aragón [Saragoza, España]
4 CEMES - Centre d'élaboration de matériaux et d'études structurales

Epitaxial strain alters the physical properties of thin films grown on single crystal substrates. Thin film oxides are particularly apt for strain engineering new functionalities in ferroic materials. In the case of La2/3Ca1/3MnO3 (LCMO) thin films, here we show the first experimental images obtained by electron holography demonstrating that epitaxial strain induces the segregation of a flat and uniform nonferromagnetic layer with antiferromagnetic (AFM) character at the top surface of a ferromagnetic (FM) layer, the whole film being chemical and structurally homogeneous at room temperature. For different substrates and growth conditions the tetragonality of LCMO at room temperature, defined as τ = |c - a|/a, is the driving force for a phase coexistence above an approximate critical value of τC ≈ 0.024. Theoretical calculations prove that the increased tetragonality changes the energy balance of the FM and AFM ground states in strained LCMO, enabling the formation of magnetically inhomogeneous states. This work gives the key evidence that opens a new route to synthesize strain-induced exchanged-biased FM-AFM bilayers in single thin films, which could serve as building blocks of future spintronic devices.

Mots clés: Phase segregations; Single crystal substrates; Nonferromagnetic layers; Theoretical calculations; Strain engineering; Electron holography; Ground state; Holography; Lanthanum compounds; Manganese oxide; Manganites; Phase separation; Single crystals; Surface segregation; Thin films; Different substrates; Epitaxial thin films; Exchange bias; Epitaxial growth

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Lorena Marín, Luis A. Rodríguez, César Magén, Etienne Snoeck, Rémi Arras, et al.. Observation of the strain induced magnetic phase segregation in manganite thin films. Nano Letters, 2015, 15 (1), pp.492-497. ⟨10.1021/nl503834b⟩. ⟨hal-01718310⟩