Dual behavior of antiferromagnetic uncompensated spins in NiFe/IrMn exchange biased bilayers

Mishra, Shrawan; Radu, F.; València, S.; Schmitz, D.; Schierle, E.; Dürr, H. A.; Eberhardt, W.

doi:10.1103/physrevb.81.212404

Cited by 50 publications

(37 citation statements)

References 36 publications

(43 reference statements)

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“…For instance, in AF/FM bilayers, the onset of EB occurs for a critical AF thickness, which is given by the condition R = (K AF t AF )/J EB ≥1, where the K AF and t AF are the anisotropy and the thickness of the AF, respectively, and J EB is the interfacial coupling constant. This implies that the AF thickness needs to be increased until the AF layer can resist the interfacial torque that acts during the rotation of the ferromagnet 15 . In our case, the thickness and the anisotropy of the HFi layer are held constant; therefore the interfacial coupling has to be decreased by increasing the thickness of the interlayer until the condition above is satisfied.…”

Section: Discussionmentioning

confidence: 99%

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Perpendicular exchange bias in ferrimagnetic spin valves

et al. 2012

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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 DyCo 5 /Ta/Fe 76 Gd 24 , where the DyCo 5 alloy has the role of a hard ferrimagnet and Fe 76 Gd 24 is a soft ferrimagnet. Taking advantage of the tunability of the exchange coupling between the ferrimagnetic layers by means of thickness variation of an interlayer spacer, we demonstrate that perpendicular unidirectional anisotropy can be induced with desirable absolute values at room temperature, without making use of a field-cooling procedure. moreover, the shift of the hysteresis loop can be reversed with relatively low magnetic fields of several hundred oersteds. This flexibility in controlling a robust perpendicular exchange bias at room temperature may be of crucial importance for applications.

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Section: Discussionmentioning

confidence: 99%

“…It was shown to be related to the anisotropic domain state of the AF system 12 . Using soft X-ray techniques, the frozen and rotatable spins 12,14,15 were observed in several systems, leading to a deeper understanding of the enhanced coercivity and the origin of the EB for systems with uncompensated AF interfaces.…”

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Perpendicular exchange bias in ferrimagnetic spin valves

et al. 2012

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“…K IrMn at RT varies from 1×10 5 to 5.5×10 5 J/m 3 . [25][26][27][28][29] Then, δ w is estimated to be 4.5 to 10.5 nm. This indicates that planar domain walls cannot form inside IrMn layer when t IrMn is less than 4. in Fig.…”

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Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

et al. 2015

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The Blocking temperature (TB) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (Heb) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of TB in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance TB and Heb. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.

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“…15,16 In addition to this, it has been observed that the coercivity and the rotatable anisotropy field show maximum values for different AF layer thicknesses. 15,[17][18][19][20][21] FM resonance has been shown to be one of the most successful techniques used to determine the values of the effective fields associated with the magnetic anisotropies in FM thin films and multilayers. [22][23][24][25][26] In addition, FMR linewidth measurements also give accurate information about the magnetic relaxation mechanisms in these systems.…”

Section: Introductionmentioning

confidence: 99%

Critical thickness investigation of magnetic properties in exchange-coupled bilayers

et al. 2011

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We present a systematic investigation of the magnetic properties of two series of polycrystalline ferromagneticantiferromagnetic bilayers (FM-AF) of Ni 81 Fe 19 (10nm)/Ir 20 Mn 80 (t AF ) grown by dc magnetron sputtering. One series was grown at an oblique angle of 50• and the other one was grown at 0• . Ferromagnetic resonance (FMR) was used to measure the exchange bias field H E , the rotatable anisotropy field H RA , and the FMR linewidth H as a function of the antiferromagnetic layer thickness t AF . Three relaxation channels due to isotropic Gilbert damping, anisotropic two-magnon scattering, and mosaicity effects are simultaneously distinguished through the angular dependence of the FMR linewidth. In the regime of small IrMn layer thicknesses, not enough to establish the exchange bias anisotropy, the FMR linewidth shows a sharp peak due to the contribution of the two-magnon scattering mechanism. The results presented here are of general importance for understanding the dynamics of magnetization in the FM-AF structures.

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Dual behavior of antiferromagnetic uncompensated spins in NiFe/IrMn exchange biased bilayers

Cited by 50 publications

References 36 publications

Perpendicular exchange bias in ferrimagnetic spin valves

Perpendicular exchange bias in ferrimagnetic spin valves

Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

Critical thickness investigation of magnetic properties in exchange-coupled bilayers

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