Seminarium Oddziału Badań Magnetyków

Tailoring the magnetic anisotropy in epitaxial ferromagnetic and antiferromagnetic films and multilayers

dr hab. Michał Ślęzak, prof. AGH

Wydział Fizyki i Informatyki Stosowanej Akademii Górniczo-Hutniczej w Krakowie

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Streszczenie:

I will present Magneto-optic Kerr Effect (MOKE), X-ray Magnetic Linear Dichroism (XMLD) as well as XMLD – PEEM (Photoemission Electron Microscope) results concerning magnetic anisotropy (MA) and spin reorientation transition (SRT) in both purely ferromagnetic (FM) and ferromagnet-antiferromagnet (FM/AFM) bilayers and multilayers epitaxially grown on W(110) single crystal.

In case of FM systems [1, 2], I will show how precise tuning of FM and non-magnetic (NM) components of the system can be used to tune the magnetic anisotropy of the ferromagnetic system. Especially quantum well states provide here possibility to induce oscillatory MA dependence on the thickness of NM overlayer [3].

In case of AFM/FM class of systems, our XMLD measurements performed at the XAS end-station in Polish synchrotron SOLARIS enabled us to follow the magnetic properties of epitaxial CoO(111)/Fe(110) [4] and NiO(111)/Fe(110) [5] bilayers. For NiO/Fe bilayers our results were additionally complemented by micro-spectroscopic and spectro-microscopic studies performed in the spectroscopic photoemission and low energy electron microscope (SPELEEM) which is the end-station of the Nanospectroscopy beamline in Elettra synchrotron (Trieste, Italy).

We find that in both studied cases FM sublayer plays a dominant role and determines the magnetic state of the neighboring AFM, however completely different interaction mechanisms are involved. In CoO/Fe bilayers the AFM spins are totally frozen although their orientation is imprinted by magnetization of Fe layer when the system passes the Neel temperature of CoO. Once the Fe layer grafts the particular MA into the CoO overlayer, it later remains frozen and insensitive to external factors like external magnetic field or Fe magnetization direction [4]. In contrast, for NiO/Fe bilayers we find that due to the weak intrinsic MA of NiO, the NiO spins are rotatable and always follow the reorientation of Fe magnetization that can be controlled by external magnetic field or via the temperature and thickness driven spin reorientation of Fe(110). In the case of the temperature induced SRT in Fe(110), it allowed us to implement all-temperature, field-free switching of AFM moments in NiO/Fe bilayers [5].

[1] Giant in-plane magnetic anisotropy in epitaxial bcc Co/Fe(110) bilayers, M. Ślęzak, T. Ślęzak, K. Matlak, B. Matlak, P. Dróżdż, T. Giela, D. Wilgocka-Ślęzak,N. Pilet, J. Raabe, A. Kozioł-Rachwał,  J. Korecki,

Physical Review B 94 (2016) 014402

[2] Multiple spin reorientation transitions and large in plane magnetic anisotropy in epitaxial Au/Co/Fe(110) films, M. Ślęzak, P. Dróżdż, K. Matlak, A. Kozioł-Rachwał, J. Korecki, T. Ślęzak

Journal of Magnetism and Magnetic Materials 475 (2019) 195–200

[3] Oscillating magnetic anisotropy in epitaxial Au/Fe(110) and Co/Au/Fe (110) films, M. Ślęzak,
P. Dróżdż, K. Matlak, A. Kozioł-Rachwał, J. Korecki, T. Ślęzak,

Journal of Magnetism and Magnetic Materials 497, 165963 (2020)

[4] How a ferromagnet drives an antiferromagnet in exchange biased CoO/Fe(110) bilayers, M. Ślęzak, T. Ślęzak, P. Dróżdż, B. Matlak, K. Matlak, A. Kozioł-Rachwał, M. Zając, J. Korecki

Scientific Reports 9 (2019) 889

[5] Fine tuning of ferromagnet/antiferromagnet interface magnetic anisotropy for field-free switching of antiferromagnetic spins, M. Ślęzak, P. Dróżdż, W. Janus, H. Nayyef, A. Kozioł-Rachwał,  M. Szpytma, M. Zając, T. O. Menteş, F. Genuzio, A. Locatelli, T. Ślęzak

Nanoscale 12 (2020) 18091-18095