Uncorrelated magnetic domains in decoupled SrFe₁₂O₁₉/Co hard/soft bilayers

TY - JOUR

T1 - Uncorrelated magnetic domains in decoupled SrFe12O19/Co hard/soft bilayers

AU - Soria, Guiomar D.

AU - Granados-Miralles, Cecilia

AU - Mandziak, Anna

AU - Jenuš, Petra

AU - Saura-Múzquiz, Matilde

AU - Christensen, Mogens

AU - Foerster, Michael

AU - Aballe, Lucía

AU - Fernández, José F.

AU - de la Figuera, Juan

AU - Quesada, Adrián

N1 - Funding Information: This work is supported by the Spanish Ministerio de Economía y Competitividad (MINECO) through Projects no. MAT2017-86450-C4-1-R, RTI2018-095303-B-C51, RTI2018-095303-B-C53, RTI2018-095303-A-C52, and FIS2017-82415-R and by the European Comission through Project H2020 no. 720853 (AMPHIBIAN). The work is funded as well by the Regional Government of Madrid through Project S2018/NMT-4321 (NANOMAGCOST). C.G.-M. acknowledges financial support from Spanish Ministerio de Ciencia e Innovación (MICINN) through the ‘Juan de la Cierva’ Program (FJC2018-035532-I). Spanish Ministerio de Economía y Competitividad (MINECO). Funding Information: This work is supported by the Spanish Ministerio de Econom?a y Competitividad (MINECO) through Projects no. MAT2017-86450-C4-1-R, RTI2018-095303-B-C51, RTI2018-095303-B-C53, RTI2018-095303-A-C52, and FIS2017-82415-R and by the European Comission through Project H2020 no. 720853 (AMPHIBIAN). The work is funded as well by the Regional Government of Madrid through Project S2018/NMT-4321 (NANOMAGCOST). C.G.-M. acknowledges financial support from Spanish Ministerio de Ciencia e Innovaci?n (MICINN) through the ?Juan de la Cierva? Program (FJC2018-035532-I). Spanish Ministerio de Econom?a y Competitividad (MINECO). Publisher Copyright: © 2020 IOP Publishing Ltd Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2021/2

Y1 - 2021/2

N2 - Composites of magnetically hard and soft phases are present in multiple and diverse applications, ranging from bulk permanent magnets in motors and generators to state-of-the-art recording media devices. The nature of the magnetic coupling between the hard and soft phases is of great technological relevance, as the macroscopic properties of the functional composite material ultimately depend on the atomic-scale interactions between phases. In this work, the hard/soft bilayer system SrFe12O19/Co has been studied based on photoemission electron microscopy combined with x-ray absorption and magnetic circular dichroism. Our experiments show that the magnetization of the hard magnetic oxide has a direction perpendicular to the layer plane, whereas the magnetization of the soft metallic overlayer remains in-plane. As a consequence, the magnetic domain patterns observed for the hard and soft phases are very different and completely uncorrelated to one another, indicating that no soft spins align with the hard phase by pure magnetodipolar arguments. The results are understood as the consequence of an absence of exchange-coupling between phases, in a scenario in which the shape anisotropy of the soft layer overcomes the Zeeman energy of the perpendicular magnetic field generated by the hard ferrite. Micromagnetic simulations of our system predict that low degrees of exchange-coupling effectively prevent substantial softening of the composite and lead to the alignment of soft and hard magnetic moments. A strategy thus emerges for the development of future hard-soft magnets, based on minimizing the degree of exchange-coupling while avoiding complete uncoupling.

AB - Composites of magnetically hard and soft phases are present in multiple and diverse applications, ranging from bulk permanent magnets in motors and generators to state-of-the-art recording media devices. The nature of the magnetic coupling between the hard and soft phases is of great technological relevance, as the macroscopic properties of the functional composite material ultimately depend on the atomic-scale interactions between phases. In this work, the hard/soft bilayer system SrFe12O19/Co has been studied based on photoemission electron microscopy combined with x-ray absorption and magnetic circular dichroism. Our experiments show that the magnetization of the hard magnetic oxide has a direction perpendicular to the layer plane, whereas the magnetization of the soft metallic overlayer remains in-plane. As a consequence, the magnetic domain patterns observed for the hard and soft phases are very different and completely uncorrelated to one another, indicating that no soft spins align with the hard phase by pure magnetodipolar arguments. The results are understood as the consequence of an absence of exchange-coupling between phases, in a scenario in which the shape anisotropy of the soft layer overcomes the Zeeman energy of the perpendicular magnetic field generated by the hard ferrite. Micromagnetic simulations of our system predict that low degrees of exchange-coupling effectively prevent substantial softening of the composite and lead to the alignment of soft and hard magnetic moments. A strategy thus emerges for the development of future hard-soft magnets, based on minimizing the degree of exchange-coupling while avoiding complete uncoupling.

KW - Hard/soft bilayers

KW - Magnetic energy

KW - Micromagnetic simulations

KW - Microscopy

KW - Strontium ferrite

KW - XMCD-PEEM

UR - http://www.scopus.com/inward/record.url?scp=85097140044&partnerID=8YFLogxK

U2 - 10.1088/1361-6463/abc0be

DO - 10.1088/1361-6463/abc0be

M3 - Journal article

AN - SCOPUS:85097140044

SN - 0022-3727

VL - 54

JO - Journal of Physics D: Applied Physics

JF - Journal of Physics D: Applied Physics

IS - 5

M1 - 054003

ER -