Manipulating magnetoelectric energy landscape in multiferroics

Yen-Lin Huang^{1

2}, Dmitri Nikonov³, Christopher Addiego⁴, Rajesh V Chopdekar⁵, Bhagwati Prasad¹, Lei Zhang¹, Jyotirmoy Chatterjee⁶, Heng-Jui Liu⁷, Alan Farhan⁸, Ying-Hao Chu⁹, Mengmeng Yang¹⁰, Maya Ramesh¹¹, Zi Qiang Qiu¹⁰, Bryan D Huey¹², Chia-Ching Lin³, Tanay Gosavi³, Jorge Íñiguez^{13

14}, Jeffrey Bokor⁶, Xiaoqing Pan^{4

15

16}, Ian Young³, Lane W Martin^{1

2}, Ramamoorthy Ramesh^{17

18

19}

Affiliations

¹ Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.
² Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA, 94720, USA.
³ Exploratory Integrated Circuits, Components Research, Intel Corp., Hillsboro, Oregon, 97124, USA.
⁴ Department of Physics and Astronomy, University of California, Irvine, Irvine, CA, 92697, USA.
⁵ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁶ Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, 94720, USA.
⁷ Department of Materials Science and Engineering, National Chung Hsing University, Taichung, 402, Taiwan.
⁸ Department of Applied Physics, Aalto University School of Science, Espoo, FI-00076, Finland.
⁹ Department of Materials Science and Engineering, National Chaio Tung University, Hsinchu, 300, Taiwan.
¹⁰ Department of Physics, University of California, Berkeley, Berkeley, CA, 94720, USA.
¹¹ Department of Physics, University of California, Irvine, Santa Cruz, CA, 95064, USA.
¹² Department of Materials Science and Engineering, University of Connecticut, Storrs, CT, 06269, USA.
¹³ Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), 5 avenue des Hauts-Fourneaux, L-4362, Esch/Alzette, Luxemburg.
¹⁴ Physics and Materials Science Research Unit, University of Luxembourg, 41, rue du Brill, L-4422, Belvaux, Luxembourg.
¹⁵ Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, 92697, USA.
¹⁶ Irvine Materials Research Institute, University of California, Irvine, Irvine, CA, 92697, USA.
¹⁷ Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹⁸ Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹⁹ Department of Physics, University of California, Berkeley, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.

PMID: 32504063
PMCID: PMC7275047
DOI: 10.1038/s41467-020-16727-2

Manipulating magnetoelectric energy landscape in multiferroics

Yen-Lin Huang et al. Nat Commun. 2020.

. 2020 Jun 5;11(1):2836.

doi: 10.1038/s41467-020-16727-2.

Authors

Affiliations

¹ Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.
² Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA, 94720, USA.
³ Exploratory Integrated Circuits, Components Research, Intel Corp., Hillsboro, Oregon, 97124, USA.
⁴ Department of Physics and Astronomy, University of California, Irvine, Irvine, CA, 92697, USA.
⁵ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁶ Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, 94720, USA.
⁷ Department of Materials Science and Engineering, National Chung Hsing University, Taichung, 402, Taiwan.
⁸ Department of Applied Physics, Aalto University School of Science, Espoo, FI-00076, Finland.
⁹ Department of Materials Science and Engineering, National Chaio Tung University, Hsinchu, 300, Taiwan.
¹⁰ Department of Physics, University of California, Berkeley, Berkeley, CA, 94720, USA.
¹¹ Department of Physics, University of California, Irvine, Santa Cruz, CA, 95064, USA.
¹² Department of Materials Science and Engineering, University of Connecticut, Storrs, CT, 06269, USA.
¹³ Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), 5 avenue des Hauts-Fourneaux, L-4362, Esch/Alzette, Luxemburg.
¹⁴ Physics and Materials Science Research Unit, University of Luxembourg, 41, rue du Brill, L-4422, Belvaux, Luxembourg.
¹⁵ Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, 92697, USA.
¹⁶ Irvine Materials Research Institute, University of California, Irvine, Irvine, CA, 92697, USA.
¹⁷ Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹⁸ Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹⁹ Department of Physics, University of California, Berkeley, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.

PMID: 32504063
PMCID: PMC7275047
DOI: 10.1038/s41467-020-16727-2

Abstract

Magnetoelectric coupling at room temperature in multiferroic materials, such as BiFeO₃, is one of the leading candidates to develop low-power spintronics and emerging memory technologies. Although extensive research activity has been devoted recently to exploring the physical properties, especially focusing on ferroelectricity and antiferromagnetism in chemically modified BiFeO₃, a concrete understanding of the magnetoelectric coupling is yet to be fulfilled. We have discovered that La substitutions at the Bi-site lead to a progressive increase in the degeneracy of the potential energy landscape of the BiFeO₃ system exemplified by a rotation of the polar axis away from the 〈111〉_pc towards the 〈112〉_pc discretion. This is accompanied by corresponding rotation of the antiferromagnetic axis as well, thus maintaining the right-handed vectorial relationship between ferroelectric polarization, antiferromagnetic vector and the Dzyaloshinskii-Moriya vector. As a consequence, La-BiFeO₃ films exhibit a magnetoelectric coupling that is distinctly different from the undoped BiFeO₃ films.

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Conflict of interest statement

The authors declare no competing interests.

Figures

**Fig. 1. Ferroelectric ordering in Bi_1−xLa_xFeO₃.**
a Schematic for the energy landscape of the phase transition induced by lanthanum substitution in BiFeO₃ described by Landau theory. b Schematic for the ferroelectric polarization rotation (from BiFeO₃: [111]_pc to Bi_0.85La_0.15FeO₃: [112]_pc) and suppression of ferroelectric polarization induced by lanthanum substitution in BiFeO₃. c *P-E* measurements for different substitution levels of lanthanum in 100-nm-thick BiFeO₃ films. d The schematics illustrate the evolution of crystal symmetry of bismuth ferrite (rhombohedral) to lanthanum ferrite (orthorhombic).

**Fig. 2. Atomic images, polarization mapping, and change of polarization in BiFeO₃ and Bi_0.85La_0.15FeO₃ thin films.**
a, b show the HAADF-STEM images of BiFeO₃ and Bi_0.85La_0.15FeO₃, respectively, with the polarization mapping of the Fe atoms overlaid. The scale bar is 1 nm. c Schematic of ferroelectric polarization in BiFeO₃/Bi_0.85La_0.15FeO₃ unit cell. The vectors in (a, b) were extracted from the displacement of Fe³⁺ position to the mass center of four Bi³⁺. d Histogram of polar distribution shows that the ferroelectric polarizations rotate 3.6°, 10.9° and 16.1° away from [111]_pc in 400-nm-thick BiFeO₃ (gray), 80-nm-thick BiFeO₃ (red) and 80-nm-thick Bi_0.85La_0.15FeO₃ (blue), respectively.

**Fig. 3. Ferroelectric switching in BiFeO₃ and Bi_0.85La_0.15FeO₃ revealed by PFM.**
a, c The as-grown IP-PFM images show different domain patterns in 20-nm-thick BiFeO₃ and Bi_0.85La_0.15FeO₃ thin films, respectively. b In-plane PFM images of 20-nm-thick BiFeO₃ after PFM electric poling with −5 V (upward polarized). d In-plane PFM images of 20-nm-thick Bi_0.85La_0.15FeO₃ after PFM electric poling with −10 V (upward polarized). The scale bar is 1 μm. e The summary of the polarization switching angles for 20-nm-thick BiFeO₃ and Bi_0.85La_0.15FeO₃ thin films. f Schematic of ferroelectric polarization switching in Bi_0.85La_0.15FeO₃ thin film.

**Fig. 4. PFM and XMLD-PEEM images of BiFeO₃ and Bi_0.85La_0.15FeO₃ thin films.**
a Schematic of the XMLD-PEEM experimental geometries used to probe the angle dependence (Φ), linear dichroism. Linear polarizations: α = 0°; Linear polarization p: α = 90°. b, c In-plane-PFM and XMLD-PEEM images of 80-nm-thick BiFeO₃. d, e In-plane-PFM and XMLD-PEEM images of 20-nm-thick BiFeO₃. f, g In-plane-PFM and XMLD-PEEM images of 80-nm-thick Bi_0.85La_0.15FeO₃. The green/red boxes represent the positive/negative polarized domain I/II. h, i In-plane-PFM and XMLD-PEEM images of 20-nm-thick Bi_0.85La_0.15FeO₃.

**Fig. 5. Magnetic anisotropy switching by electric field via the heterostructure of spin-valve/BiFeO₃ (Bi_0.85La_0.15FeO₃).**
a Schematics for the different electrically polarized states of P, L, and M_C in BiFeO₃ and Bi_0.85La_0.15FeO₃. b Schematic for magnetoresistance measurements on spin-valve/BiFeO₃ (Bi_0.85La_0.15FeO₃) heterostructure. c R(H) of spin-valve/BiFeO₃ on the different electrically polarized states. d micromagnetic simulations on R(H) of spin-valve/BiFeO₃ with different polarization states. e R(H) of spin-valve/ Bi_0.85La_0.15FeO₃ on the different electrically polarized states. f Micromagnetic simulations on R(H) of spin-valve/ Bi_0.85La_0.15FeO₃ with different polarization states.

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References

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Manipulating magnetoelectric energy landscape in multiferroics

Affiliations

Manipulating magnetoelectric energy landscape in multiferroics

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

References

Grants and funding

LinkOut - more resources

Full Text Sources

Research Materials