Articolele autorului Florin Radu
Link la profilul stiintific al lui Florin Radu

Perpendicular exchange bias in ferrimagnetic spin valves

The exchange bias effect refers to the shift of the hysteresis loop of a ferromagnet in direct contact to an antiferromagnet. For applications in spintronics a robust and tunable exchange bias is required. Here we show experimental evidence for a perpendicular exchange bias in a prototypical ferrimagnetic spin valve consisting of DyCo5/Ta/Fe76Gd24, where the DyCo5 alloy has the role of a hard ferrimagnet and Fe76Gd24 is a soft ferrimagnet. Taking

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Dual Behavior of Antiferromagnetic Uncompensated Spins in NiFe/IrMn Ex- change Biased Bilayers

We present a comprehensive study of the exchange bias effect in a model system. Through numerical analysis of the exchange bias and coercive fields as a function of the antiferromagnetic layer thickness we deduce the absolute value of the averaged anisotropy constant of the antiferromagnet. We show that the anisotropy of IrMn exhibits a finite size effect as a function of thickness. The interfacial spin disorder involved in the data analysis is further

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Interface-induced room-temperature multiferroicity in BaTiO3

Multiferroic materials possess two or more ferroic orders but have not been exploited in devices owing to the scarcity of room-temperature examples. Those that are ferromagnetic and ferroelectric have potential applications in multi-state data storage if the ferroic orders switch independently, or in electric-field controlled spintronics if the magnetoelectric coupling is strong. Future applications could also exploit toroidal moments and optical

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Origin of the reduced exchange bias in an epitaxial FeNi(111)/CoO(111) bilayer

We have employed soft and hard x-ray resonant magnetic scattering and polarized neutron diffraction to study the magnetic interface and the bulk antiferromagnetic domain state of the archetypal epitaxial Ni81Fe19(111)/CoO(111) exchange biased bilayer. The combination of these scattering methods provides unprecedented detailed insights into the still incomplete understanding of some key manifestations of the exchange bias effect. We show that the

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Training-Induced Positive Exchange Bias in NiFe/IrMn Bilayers
Exchange bias effect of ferro-/antiferromagnetic heterostructures

The exchange bias effect, discovered more than fifty years ago, is a fundamental interfacial property, which occurs between ferromagnetic and antiferromagnetic materials. After intensive experimental and theoretical research over the last ten years, a much clearer picture has emerged about this effect, which is of immense technical importance for magneto-electronic device applications. In this review we start with the discussion of numerical and

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Quantitative description of the azimuthal dependence of the exchange bias effect

While the principal features of the exchange bias between a ferromagnet and an antiferromagnet are believed to be understood, a quantitative description is still lacking. We show that interface spin disorder is the main reason for the discrepancy of model calculations versus experimental results. Taking into account spin disorder at the interface between the ferromagnet and the antiferromagnet by modifying the well known Meiklejohn and Bean model,

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Reversing the Training Effect in Exchange Biased CoO/Co Bilayers

We performed a detailed study of the training effect in exchange biased CoO/Co bilayers. Highresolution measurements of the anisotropic magnetoresistance (AMR) display an asymmetry in the first magnetization reversal process and training in the subsequent reversal processes. Surprisingly, the AMR measurements as well as magnetization measurements reveal that it is possible to partially reinduce the untrained state by performing a hysteresis measurement

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Fundamental Aspects of Exchange Bias Effect

This thesis is organized in three parts: "Fundamentals of Exchange Bias", "Polarized Neutron Reflectometry", and "Exchange Bias in CoO/Ferromagnet Bilayers and Multilayers". In the first part, some of the current models for exchange bias are reviewed and a new model is developed. In the second part of the thesis some fundamental aspects of polarized neutron reflectometry and its applications to magnetic thin films and heterostructures are described.

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Cum se “rotesc” neutronii

Cum se comporta neutronii intr-un strat magnetic foarte subtire atunci cand momentul lor magnetic interactioneaza cu acesta? Acestei intrebari de fizica fundamentala i-a gasit raspuns Florin Radu (Catedra de Fizica Experimetala, Fizica Solidului condusa de Prof. Dr. Dr. h. c. Hartmut Zabel) cu ajutorul experimentelor si modelelor teoretice. Cercetatorii au putut arata ca dupa ce neutronii patrund in stratul magnetic, momentul magnetic al acestora

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