Direct observation of temperature-driven magnetic symmetry transitions by vectorial resolved MOKE magnetometry

Cuñado, J. L. F.; Pedrosa, Javier; Ajejas, Fernando; Perna, Paolo; Miranda, Rodolfo; Camarero, Julio

doi:10.1088/1361-648x/aa7f45

Cited by 4 publications

(1 citation statement)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the analysis of this kind of magnetic anisotropy competition is complex. A detailed model system with competing anisotropies can be found in [33,34].…”

Section: Resultsmentioning

confidence: 99%

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Lorenzo-Feijoo,

Serrano,

Hernández-Gómez

et al. 2024

Crystals

View full text Add to dashboard Cite

Antiferromagnetic/ferromagnetic (AF/F) systems have been extensively investigated due to the importance that interfacial exchange coupling effects have in the development of magnetic storage technologies. Recently, these systems have garnered interest for the potential they have to imprint the magnetic moments of the AF into an F layer, offering the possibility of using it as a read-out mechanism in antiferromagnetic spintronics. In this study, we explored the importance of crystalline orientation and strains induced by the substrate in the exchange coupling properties of NiO/FeCo AF/F bilayers. For that, we have grown NiO/FeCo bilayers on MgO (001) and Al2O3 (0001) substrates varying the FeCo layer thickness. In addition, we have analyzed both deposited samples and those with induced interfacial unidirectional anisotropy. For inducing such interfacial anisotropy, we used a field cooling procedure, heating the bilayers to 650 K and subsequently cooling down to room temperature under the presence of an external magnetic field of 300 mT. We have investigated the effect of the substrate in terms of crystalline orientation and lattice mismatching on the AF/F exchange coupling as well as the dependence of the coercivity and exchange bias on the inverse F layer thickness that is consistent with the interfacial origin of the AF/F exchange coupling. Moreover, the angular dependence of the magnetic properties was explored by using vectorial Kerr magnetometry, confirming the presence of both magnetocrystalline anisotropy, arising from the epitaxial character of the growing process mainly when the bilayer is grown on MgO (001) substrates, and the field cooling (FC)-induced unidirectional anisotropy.

show abstract

“…However, the analysis of this kind of magnetic anisotropy competition is complex. A detailed model system with competing anisotropies can be found in [33,34].…”

Section: Resultsmentioning

confidence: 99%

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Lorenzo-Feijoo,

Serrano,

Hernández-Gómez

et al. 2024

Crystals

View full text Add to dashboard Cite

show abstract

Interfacial Exchange Phenomena Driven by Ferromagnetic Domains

Díez

Cuñado

Lapa

et al. 2022

Adv Materials Inter

Self Cite

View full text Add to dashboard Cite

to control most of the new properties observed in these artificial systems. [1] Despite the increasing progress in applications, a satisfactory microscopic knowledge of some fundamental physical aspects is still lacking. Paradigmatic is the case of the exchange interaction at the interface between an antiferromagnet (AFM) and a ferromagnet (FM), [2] which is used in most spintronic devices to pin (or stabilize) the magnetization of the adjacent thin FM film although there are still puzzles and experimental contradictions not well understood about its origin and effects. [2,3] The interfacial exchange coupling in AFM/FM systems was discovered and initially described by Meiklejohn and Bean in 1956. [4] Experimentally, when an AFM/ FM heterostructure is field cooled (FC) from above the Néel temperature (T N ) of the AFM layer, [2,4] and this undergoes the phase transition with the FM layer oriented in a certain direction, [5] an interfacial unidirectional anisotropy (K E ) is induced, which shifts the hysteresis loop away from zero field by the exchange bias field H E . The naivest picture fails in predicting a value of H E orders of magnitude larger than observed, or its vanishing at T N (while it often occurs at a smaller temperature, referred as blocking temperature T B ≤ T N .) The simple picture does not explain effects on the coercive field Interfacial proximity effects in antiferromagnetic/ferromagnetic (AFM/FM) bilayers control the exchange-bias (EB) phenomena exploited in most spintronic devices, although still is lack of full understanding. Discordant results, including different exchange-bias field (H E ), coercivity (H C ), or blocking temperature (T B ) found even in similar systems, are usually ascribed to uncontrolled parameters, namely dissimilar interfacial defects, structure, and thicknesses. Here, it is shown in the very same sample that the magnetic domain structure during the magnetization reversal of the FM layer controls those mentioned effects. Simultaneous transport and vectorial-resolved magnetic measurements performed in a V 2 O 3 /Co system during warming after different field cooling (FC) procedures exhibit a strong dependence on the FC angle and the domain structure of the FM layer. Remarkably, magnetization reversal analysis reveals 35 K of variation in T B and up to a factor of two in H E . These observations can be explained within the random-field model for the interfacial exchange coupling with a fixed AFM domain structure in contact with a variable (angle-dependent) FM domain structure. The results highlight the importance of the domain structure and magnetization reversal of the FM layer (not previously considered) in the EB phenomena, with potential to tailor interfacial effects in future spintronic devices.

show abstract