The microstructural evolution of chemical disorder and ferromagnetism in He+ irradiated FePt3 films

Causer, Grace L.; Zhu, Hanliang; Davis, Joel; Ionescu, Mihail; Mankey, G. J.; Wang, Xiaotian; Klose, F.

doi:10.1016/j.apsusc.2018.08.028

Cited by 6 publications

(2 citation statements)

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“…In recent years, ion-beam engineering has proven a highly efficient method for inducing nanometer-precise chemical and magnetic modifications in a wide class of materials. [2][3][4][5][6][7][8][9] Magnetic multilayers often employ the phenomenon of exchange bias by utilizing the competing magnetic interactions between neighboring ferromagnetic (FM) and antiferromagnetic (AF) nanocrystalline layers. An exchange biased state is induced when the magnetization of the FM layer becomes pinned through magnetic interactions at the chemical interface to the AF layer, if the temperature of the system is cooled below the transition temperature of the AF component.…”

Section: Introductionmentioning

confidence: 99%

The magnetic interfacial properties of an exchange biased nanocrystalline Ni₈₀Fe₂₀/α-Fe₂O₃ bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

Causer

Cortie

Callori

et al. 2019

Jpn. J. Appl. Phys.

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The strength of exchange bias can be influenced by interface roughness and antiferromagnetic morphology. Here, we studied the interface profile of an exchange biased, nanocrystalline Ni80Fe20/α-Fe2O3 bilayer. Magnetometry determined the bilayer’s exchange bias is observed below a blocking temperature of 75 K. Polarized neutron reflectometry measurements revealed the Ni80Fe20 layer was fully saturated to yield a net-moment of 0.95 μB/atom, while the majority of the Fe2O3 layer exhibited zero net-magnetization with the exception of the interfacial region with an uncompensated moment between 0.5 and 1.0 μB/Fe2O3. Monte Carlo simulations of a ferromagnetic/antiferromagnetic bilayer incorporating a granular antiferromagnet indicate that an extrinsic uncompensated moment of ∼1.0 μB/Fe2O3 can arise from grain boundary disorder. The size of the modeled moment is equivalent to the experimental value, and comparable with previous calculations. Furthermore, unlike intrinsic uncompensated spins, it is found that the disorder-induced moment in the granular antiferromagnet is not destroyed by interface roughness.

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Section: Introductionmentioning

confidence: 99%

The magnetic interfacial properties of an exchange biased nanocrystalline Ni₈₀Fe₂₀/α-Fe₂O₃ bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

Causer

Cortie

Callori

et al. 2019

Jpn. J. Appl. Phys.

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“…[254]- [257] Increase 1. Interfacial Mixing [205], [227], [258], [259] 3.1.2 Modification in Antiferromagnetic Thin-Films and Exchange Bias…”

Section: Modification In Ferromagnetic Thin Films and Multilayer Stacksmentioning

confidence: 99%

Defect Engineering Of Perpendicular Magnetic Anisotropy In Cobalt-Based Thin Films

Mahendra

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Magnetic sensors have widespread applications in industrial, security, space, and biomedical fields, offering precise measurement of magnetic fields using principles like the Hall effect and magnetoresistance. Magnetic tunnel junctions (MTJs) have played a pivotal role in advancing magnetic sensing through tunnelling magnetoresistance (TMR), contributing to spintronic devices, memory systems, and magnetic sensors. The magnetic anisotropy of the reference ferromagnetic layer in MTJ sensors is a critical factor, influencing sensitivity, accuracy, and sensing direction. Perpendicular magnetic anisotropy (PMA) is particularly advantageous for detecting magnetic fields perpendicular to the sensor plane, opening possibilities in non-destructive testing and magnetic read heads. However, conventional sensors are restricted to fixed axes, hindering their ability to measure fields in three dimensions. To address this limitation, this thesis proposes a magnetic sensor with a tuneable sensing axis, enabling comprehensive field detection in all axes. As part of this exploration, the thesis investigates ion irradiation as a post-processing technique to modify the PMA of ferromagnetic layers, offering versatility for various applications.Cobalt-based materials, especially CoFeB, are well-known for their suitability in MTJs due to high TMR with MgO and PMA at low thicknesses. Half-metallic Heusler alloys, like Co2MnGa, have gained attention for their theoretically infinite TMR, high spin polarization, and high PMA. This research assesses the effects of ion irradiation on ultra-thin Co2MnGa and CoFeB stacks with PMA.Ion irradiation is a versatile tool for precisely tailoring magnetic stack properties with uniformity and reproducibility. This thesis investigates the impact of 30 keV Ar and Ne ion irradiation on CoFeB and Co2MnGa thin film stacks at low fluences (1 × 1013 to 1 × 1015 ion·cm−2), introducing displacement per atom (DPA) as a predictive parameter for ion-induced magnetic property changes. Results show a consistent reduction in PMA for both materials in half-MTJ stacks after irradiation, which is linked to intermixing of the magnetic layer with its adjacent MgO and heavy metal layers. Ar irradiation has a more pronounced effect due to higher DPA, while Ne irradiation has a milder impact. Co2MnGa displays relatively more resilience to irradiation due to reduced intermixing with adjacent layers, compared to CoFeB. Furthermore, the thesis explores the dynamic tuning of magnetic properties through ionic liquid gating, allowing anisotropy and coercivity manipulation via voltage control. It also delves into ion irradiation's potential to enhance the magneto-ionic effect. Lastly, a novel magnetic sensor design is introduced featuring a tuneable sensing axis, enabling three-dimensional detection capabilities.

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Tailoring of magnetic anisotropy by ion irradiation for magnetic tunnel junction sensors

Mahendra

Gupta

Granville

et al. 2022

Journal of Alloys and Compounds

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The microstructural evolution of chemical disorder and ferromagnetism in He+ irradiated FePt3 films

Cited by 6 publications

References 21 publications

The magnetic interfacial properties of an exchange biased nanocrystalline Ni₈₀Fe₂₀/α-Fe₂O₃ bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

The magnetic interfacial properties of an exchange biased nanocrystalline Ni₈₀Fe₂₀/α-Fe₂O₃ bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

Defect Engineering Of Perpendicular Magnetic Anisotropy In Cobalt-Based Thin Films

Tailoring of magnetic anisotropy by ion irradiation for magnetic tunnel junction sensors

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The microstructural evolution of chemical disorder and ferromagnetism in He+ irradiated FePt3 films

Cited by 6 publications

References 21 publications

The magnetic interfacial properties of an exchange biased nanocrystalline Ni80Fe20/α-Fe2O3 bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

The magnetic interfacial properties of an exchange biased nanocrystalline Ni80Fe20/α-Fe2O3 bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

Defect Engineering Of Perpendicular Magnetic Anisotropy In Cobalt-Based Thin Films

Tailoring of magnetic anisotropy by ion irradiation for magnetic tunnel junction sensors

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The magnetic interfacial properties of an exchange biased nanocrystalline Ni₈₀Fe₂₀/α-Fe₂O₃ bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

The magnetic interfacial properties of an exchange biased nanocrystalline Ni₈₀Fe₂₀/α-Fe₂O₃ bilayer studied by polarized neutron reflectometry and Monte Carlo simulation