Sign of the spin-polarization in cobalt-iron nitride films determined by the anisotropic magnetoresistance effect

Ito, Keita; Kabara, Kazuki; Sanai, Tatsunori; Toko, Kaoru; Imai, Yoji; Tsunoda, Masakiyo; Suemasu, Takashi

doi:10.1063/1.4892179

Cited by 41 publications

(44 citation statements)

References 41 publications

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“…In the case of Fe-N, the phase diagram is well-known and the Fe 4 N phase is formed at T s ∼ 623 K. In the absence of Co-N phase diagram, the experimental method adopted for preparation of Co 4 N thin film seems to be influenced directly by the recipe used for Fe 4 N thin films. However there seems to be large variations in T s used for preparation of Co 4 N thin films; T s as large as 723 T s as low as 300 K [2,3,5,6,27]. In a recent work, It was demonstrated that Co 4 N thin film with lattice parameter close to its theoretical values can be prepared at 300 K and these films were not stable beyond 473 K [27].…”

Section: Introductionmentioning

confidence: 99%

“…Fe 4 N, Co 4 N) are ferromagnetic materials having higher (than pure metal) magnetic moment, large spin polarization ratio (SPR) and superior chemical stability. Such properties make them a candidate in high density magnetic memory devices and spintronics [1,2,3,4,5,6]. In addition, transition metal nitrides are also used as an anode materials for lithium-ion batteries.…”

Section: Introductionmentioning

confidence: 99%

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Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K

Pandey

Gupta

et al. 2017

Journal of Alloys and Compounds

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In this work, we studied cobalt nitride (Co-N) thin films deposited using a dc magnetron sputtering method at a substrate temperature (T s ) of 523 K. We find that independent of the reactive gas flow (R N 2 ) used during sputtering, the phases of Co-N formed at this temperature seems to be identical having N at.% ∼5. This is contrary to Co-N phases formed at lower T s . For T s ∼300 K, an evolution of Co-N phases starting from Co(N)→Co 4 N→Co 3 N→CoN can be seen as R N 2 increases to 100%, whereas when the substrate temperature increases to 523 K, the phase formed is a mixture of Co and Co 4 N, independent of the R N 2 used during sputtering. We used x-ray diffraction (XRD) to probe long range ordering, x-ray absorption spectroscopy (XAS) at Co absorption edge for the local structure, Magneto-optical Kerr e ffect (MOKE) and polarized neutron reflectivity (PNR) to measure the magnetization of samples. Quantification of N at.% was done using secondary ion mass spectroscopy (SIMS). Measurements suggest that the magnetic moment of Co-N samples deposited at 523 K is slightly higher than the bulk Co moment and does not get affected with the R N 2 used for reactive sputtering. Our results provide an important insight about the phase formation of Co-N thin films which is discussed in this work.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K

Pandey

Gupta

et al. 2017

Journal of Alloys and Compounds

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“…Compared to the Fe-N, the Co-N system is any way less explored. [11][12][13][14][15][16][17][18][19] Recent theoretical calculations predicted that the spin polarization ratio for Co 4 N is even higher than that of Fe 4 N. 20,21 This has led to somewhat renowned interests in the Co-N system both theoretically and experimentally. [22][23][24][25][26][27][28] Though theoretical studies predict that under large-volume high-moment approach, the magnetic moment of Co 4 N can be larger than Co, 9 experimental results always find a value much smaller than pure Co, for Co 4 N thin films.…”

Section: Introductionmentioning

confidence: 99%

Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

et al. 2015

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Cobalt nitride (Co-N) thin films prepared using a reactive magnetron sputtering process are studied in this work. During the thin film deposition process, the relative nitrogen gas flow (RN2) was varied. As RN2 increases, Co(N), Co4N, Co3N and CoN phases are formed. An incremental increase in RN2, after emergence of Co4N phase at RN2 = 10%, results in a linear increase of the lattice constant (a) of Co4N. For RN2 = 30%, a maximizes and becomes comparable to its theoretical value. An expansion in a of Co4N, results in an enhancement of the magnetic moment, to the extent that it becomes even larger than pure Co. Such larger than pure metal magnetic moment for tetra-metal nitrides (M4N) have been theoretically predicted. Incorporation of N atoms in M4N configuration results in an expansion of a (relative to pure metal) and enhances the itinerary of conduction band electrons leading to larger than pure metal magnetic moment for M4N compounds. Though a higher (than pure Fe) magnetic moment for Fe4N thin films has been evidenced experimentally, higher (than pure Co) magnetic moment is evidenced in this work.

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“…1 Extensive studies have been performed on the magnetic and transport properties of Fe 4 N after this report. [2][3][4][5][6][7][8][9][10][11][12] The spin polarization of Fe 4 N has been experimentally confirmed by point contact Andreev reflection (PCAR) on a (100) oriented Fe 4 N thin film. 2 Magnetic tunnel junctions (MTJ) with Fe 4 N ferromagnetic electrodes has been reported and their MR ratios are as large as 75% at room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…3,4 Furthermore, unlike the conventional ferromagnetic electrodes such as CoFeB and CoFe, Fe 4 N has also been predicted and experimentally proved to be a negative spin polarized material. [5][6][7] This characteristic provides a pathway for some novel spin-logic devices. 8,9 To date, most of the spintronics related studies on Fe 4 N are based on epitaxial or polycrystalline thin films with (100) out-of-plane orientation.…”

Section: Introductionmentioning

confidence: 99%

Deposition and spin polarization study of Fe4N thin films with (111) orientation

Osofsky

Jensen

et al. 2017

AIP Advances

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We have successfully deposited Fe4N thin films with (111) out-of-plane orientation on thermally oxidized Si substrates using a facing-target-sputtering system. A Ta/Ru composite buffer layer was adopted to improve the (111) orientation of the Fe4N thin films. The N2 partial pressure and substrate temperature during sputtering were optimized to promote the formation of the Fe4N phase. Furthermore, we measured the transport spin polarization of (111) oriented Fe4N by the point contact Andreev reflection (PCAR) technique. The spin polarization ratio was determined to be 0.50 using a modified BTK model. The film thickness dependence of the spin polarization was also investigated. The spin polarization of Fe4N measured by PCAR does not show degradation as the sample thickness was reduced to 10nm.

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Sign of the spin-polarization in cobalt-iron nitride films determined by the anisotropic magnetoresistance effect

Cited by 41 publications

References 41 publications

Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K

Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K

Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

Deposition and spin polarization study of Fe4N thin films with (111) orientation

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