Microscopic study of thermally and electrically driven magnetic changes in La 0.7 Sr 0.3 MnO 3 films on BaTiO 3 substrates

Epitaxial films of the ferromagnetic manganite <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi mathvariant="normal">La</a:mi> <a:mrow> <a:mn>0.7</a:mn> </a:mrow> </a:msub> <a:msub> <a:mi mathvariant="normal">Sr</a:mi> <a:mrow> <a:mn>0.3</a:mn> </a:mrow> </a:msub> <a:msub> <a:mi>MnO</a:mi> <a:mn>3</a:mn> </a:msub> </a:mrow> </a:math> on substrates of the ferroelectric perovskite <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:msub> <d:mi>BaTiO</d:mi> <d:mn>3</d:mn> </d:msub> </d:mrow> </d:math> are known to display sharp magnetic changes and large magnetoelectric effects when the film is strained by the substrate undergoing thermally driven structural transitions and ferroelectric domain switching, respectively. However, only a single component of the in-plane magnetization has been hitherto imaged. Here we present magnetic vector maps—obtained from photoemission electron microscopy images with magnetic contrast from x-ray magnetic circular dichroism—to show that the electrically and thermally driven changes of local and global magnetization are deterministically influenced by the state of the substrate while also being complex and sample dependent. Our findings, supported by ferromagnetic resonance data and vibrating sample magnetometry, reveal that the behavior of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:msub> <e:mi mathvariant="normal">La</e:mi> <e:mrow> <e:mn>0.7</e:mn> </e:mrow> </e:msub> <e:msub> <e:mi mathvariant="normal">Sr</e:mi> <e:mrow> <e:mn>0.3</e:mn> </e:mrow> </e:msub> <e:msub> <e:mi>MnO</e:mi> <e:mn>3</e:mn> </e:msub> </e:mrow> </e:math> films on <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mrow> <h:msub> <h:mi>BaTiO</h:mi> <h:mn>3</h:mn> </h:msub> </h:mrow> </h:math> substrates is not well predicted from knowledge of each system, probably due to long-range strain between <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mrow> <i:msub> <i:mi>BaTiO</i:mi> <i:mn>3</i:mn> </i:msub> </i:mrow> </i:math> domains. In the future, it would be interesting to reduce complexity by patterning the film into regions between which magnetic communication is negligible.