Strong correlation between uniaxial magnetic anisotropic constant and in-plane tensile strain in Mn4N epitaxial films

Hirose, Taku; Komori, Taro; Gushi, Toshiki; Anzai, Akihito; Toko, Kaoru; Suemasu, Takashi

doi:10.1063/1.5141818

Cited by 32 publications

(24 citation statements)

References 39 publications

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“…The Mn-atoms at the corner and the face center have inequivalent magnetic moments and are ferrimagnetically coupled 21 . Although the easy axis of bulk Mn4N is along the [111] direction, PMA is repeatedly and reproducibly observed in crystalline Mn4N films [22][23][24][25][26][27][28] . As a result, ferrimagnetic Mn4N thin films have also attracted increasing interest in spintronics applications.…”

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confidence: 87%

“…As noted earlier, the emergence of PMA is an important magnetic property for its use in spintronic applications. One of the plausible reasons for the PMA in Mn4N thin films could be attributed to the deviation of the out-of-plane lattice constant, c, to the in-plane lattice constant, a, (c/a) ratio from 1, [22][23][24][25][26][27][28] due to the in-plane epitaxial strain. A recent study also showed that the anisotropy energy is correlated to the c/a ratio 27 .…”

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confidence: 99%

“…One of the plausible reasons for the PMA in Mn4N thin films could be attributed to the deviation of the out-of-plane lattice constant, c, to the in-plane lattice constant, a, (c/a) ratio from 1, [22][23][24][25][26][27][28] due to the in-plane epitaxial strain. A recent study also showed that the anisotropy energy is correlated to the c/a ratio 27 . We note that further studies are warranted to understand the interplay of magnetic and strain effects on the PMA and this is beyond the scope of this paper.…”

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confidence: 99%

“…Several groups have grown crystalline Mn4N epitaxial films (30-100 nm) on MgO, SrTiO3, or LaAlO3 substrates by magnetron sputtering 22,23 , molecular beam epitaxy (MBE) [24][25][26][27] , and pulsed laser deposition (PLD) 28 , and they reported similar c/a ratios of ~0.99. The reported uniaxial magnetic anisotropy constant (Ku) and Ms of those Mn4N films were about 0.5-1 Merg/cc and 50-100 emu/cc, respectively [22][23][24][25][26][27][28] , comparable with the data observed for amorphous GdCo thin films (Ku ~ 0.25 Merg/cc and Ms ~ 50 emu/cc) 12 .…”

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confidence: 99%

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Rare-earth-free ferrimagnetic Mn4N sub-20 nm thin films as potential high-temperature spintronic material

Zhou

Hartnett

et al. 2021

AIP Advances

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Ferrimagnetic alloy thin films that exhibit perpendicular (out-of-plane) magnetic anisotropy (PMA) with low saturation magnetization, such as GdCo and Mn4N, were predicted to be favorable for hosting small Néel skyrmions for room temperature applications. Due to the exponential decay of interfacial Dzyaloshinskii-Moriya interaction (DMI) and the limited range of spin-orbit-torques, which can be used to drive skyrmion motion, the thickness of the ferrimagnetic layer has to be small, preferably under 20 nm. While there are examples of sub-20 nm, rare earth-transition metal (RE-TM), ferrimagnetic thin films fabricated by sputter deposition, to date rare-earth-free sub-20 nm Mn4N films with PMA have only been reported to be achieved by molecular beam epitaxy, which is not suitable for massive production. Here we report the successful thermal growth of sub-20 nm Mn4N films with PMA at 400-450 °C substrate temperatures on MgO substrates by reactive sputtering. The Mn4N films were achieved by reducing the surface roughness of MgO substrate through a high-temperature vacuum annealing process. The optimal films showed low saturation magnetization (Ms = 43 emu/cc), low magnetic anisotropy energy (0.7 Merg/cc), and a remanent magnetization to saturation magnetization ratio (Mr/Ms) near 1 at room temperature. Preliminary ab-initio density functional theory (DFT) calculations have confirmed the ferrimagnetic ground state of Mn4N grown on MgO. The magnetic properties, along with the high thermal stability of Mn4N thin films in comparison with RE-TM thin films, provide the platform for future studies of practical skyrmion-based spintronic materials.

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confidence: 87%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Rare-earth-free ferrimagnetic Mn4N sub-20 nm thin films as potential high-temperature spintronic material

Zhou

Hartnett

et al. 2021

AIP Advances

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“…One promising candidate with superior thermal stability compared to the amorphous rare-earth transition metals is rare-earth-free Mn 4 N. There are some key similarities and differences between the rare-earth transition metals and Mn 4 N. Both are ferrimagnetic metals, and there have been successful experimental demonstrations of thin film growth in both systems. Both materials show perpendicular magnetic anisotropy (PMA) in the thin film geometry 16,[20][21][22][23][24][25][26][27] . However, unlike the amorphous structure in the rare-earth transition metals, Mn 4 N is a crystalline compound that forms in the anti-perovskite crystal structure 27 .…”

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confidence: 99%

Tunable Magnetic Skyrmions in Ferrimagnetic Mn$_4$N

Ma,

Hartnett,

Zhou

et al. 2021

Preprint

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Thin films of ferrimagnetic Mn 4 N are candidate materials to host magnetic skyrmions that have demonstrated thermal stability up to 450 • C. However, there are no experimental reports observing skyrmions in this system. Here, we discuss the results of sputter grown 15-17 nm Mn 4 N thin films on MgO substrate capped with Pt 1−x Cu x layers. Vibrating sample magnetometry measurement of out-of-plane hysteresis loops confirmed that magnetic properties are insensitive to the cap layer composition. Imaging based on magnetic force microscopy measurements observed 300 to 50 nm sized skyrmions, as the Cu concentration was increased from x = 0 to 0.9. We performed density functional theory calculations and found that the interfacial Dzyaloshinskii-Moriya interactions (iDMI) follow a trend: Mn 4 N/MgO(001) < Cu/Mn 4 N(001) < Pt/Mn 4 N(001). We infer from these calculations that x in Pt 1−x Cu x capping layer can serve as a robust tuning knob to tailor the iDMI and control the skyrmion size. This work provides guidance to achieve smaller Néel-type skyrmions in Mn 4 N thin films, which is an important step forward for building thermally stable skyrmionic devices.

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Rare-earth-free noncollinear metallic ferrimagnets Mn4-xZxN with compensation at room temperature

Zhang

Fruchart

et al. 2022

Acta Materialia

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Strong correlation between uniaxial magnetic anisotropic constant and in-plane tensile strain in Mn4N epitaxial films

Cited by 32 publications

References 39 publications

Rare-earth-free ferrimagnetic Mn4N sub-20 nm thin films as potential high-temperature spintronic material

Rare-earth-free ferrimagnetic Mn4N sub-20 nm thin films as potential high-temperature spintronic material

Tunable Magnetic Skyrmions in Ferrimagnetic Mn$_4$N

Rare-earth-free noncollinear metallic ferrimagnets Mn4-xZxN with compensation at room temperature

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