Comparative investigation of structural and transport properties of L1<sub>0</sub>NiPt and CoPt phases; the role of magnetism

Leroux, C.; Cadeville, M.C.; Pierron‐Bohnes, V.; Inden, Gerhard; Hinz, F

doi:10.1088/0305-4608/18/9/021

Cited by 156 publications

(104 citation statements)

References 30 publications

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Section: Disorder-order Transformation Under Zero Magnetic Field and supporting

confidence: 90%

“…2 also include the information of the order-disorder transformation temperature, T (o-d) , and the disorder-order transformation temperature, T (d-o) . In the case of the Co-50Pt alloy, 1 095 K, being consistent with 1 100 K reported by Leroux et al,13) andfor the Fe-55Pd alloy (70 K) is larger than that for the Co-50Pt alloy (50 K), meaning that nucleation of the ordered L1 0 -phase requires larger supercooling in the Fe-55Pd alloy compared with the Co-50Pt alloy.Incidentally, we notice in Fig. 2(a) that the resistivity of the disordered phase (solid curve) coincides with the resistivity of the ordered phase (open marks) at about 1 000 K and higher.…”

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Ordering Process and Variant Selection under Magnetic Field in L10-type Co–50Pt and Fe–55Pd Alloys

2009

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Selected formation of variants under magnetic field in a diffusional process has been investigated by using Co-50Pt (at%) and Fe-55Pd (at%) alloys exhibiting A1 (disorder)-L1 0 (order) transformations. A single variant of the ordered phase is obtained in these alloys by applying a magnetic field during the early stage of ordering. The lowest magnetic field required for obtaining the single variant is about 0.5 T for the Co-50Pt alloy, and 4 T for the Fe-55Pd alloy in the present heat-treatment conditions. Such a difference could be due to the relation between nucleation barrier for the formation of the ordered phase and magnetocrystalline anisotropy at the nucleation stage.KEY WORDS: cobalt-platinum alloy; iron-palladium alloy; Curie temperature; single variant; magnetocrystalline anisotropy.Y-, Z-variants, respectively, and these fractions as f x , f y , and f z . The fraction of each variant was determined by magnetization measurements using a SQUID magnetometer. When the specimen is highly ordered, the fraction will be obtained by using the relation f x ϭM x 0 /M s , f y ϭM y 0 /M s , f z ϭM z 0 /M s ; where M s is the spontaneous magnetization; M x 0 , M y 0 , M z 0 , are the magnetization at zero field extrapolated from the high field region measured along the X-, Y-, Z-directions, respectively. Results Disorder-Order Transformation under Zero Magnetic Field and Magnetic PropertiesIn this section, we will show the ordering process in Co-50Pt and Fe-55Pd alloys in the absence of magnetic field and determine the Curie temperatures of their disorder and order phases.First, time evolution of disorder-order transformation has been examined by measuring electrical resistivity at 273 K after performing an isothermal heat-treatment at different ordering temperatures followed by quenching into ice-water. The result is shown in Fig. 1, where the resistivity is normalized by the value of the as-quenched specimen, r A.Q. at 273 K. In the case of the Co-50Pt alloy, the resistivity saturates within 3 h by the heat-treatment at 1 023 K, while not within 200 h by the heat-treatment at 973 K, 873 K, and 773 K. These results imply that the ordering process is the fastest at 1 023 K and slowest at 773 K in the examined temperature range. Similar results were reported by Newkirk et al. 10) in a Co-48Pt (at%) alloy. In the case of Fe-55Pd alloy, the resistivity saturates within 3 h by the heat-treatment at 873 K, within 21 h at 773 K, while not within 163 h by heat-treatment at 673 K.Second, we examined the Curie temperature of the disordered phase by electrical resistivity measurement. The measurements were made by heating the disordered specimen from room temperature with a heating rate of 100 K/min, and the result is shown in Fig. 2 by solid curves. In the case of the Co-50Pt alloy (a), the resistivity heating curve exhibits a bending as indicated by an arrow at about 850 K. We can interpret this temperature as the Curie temperature of the disordered phase, T c (d) , considering the same bending appears at Curie tempera...

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Section: Disorder-order Transformation Under Zero Magnetic Field and supporting

confidence: 90%

supporting

confidence: 89%

Ordering Process and Variant Selection under Magnetic Field in L10-type Co–50Pt and Fe–55Pd Alloys

2009

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“…Most prominent is the β 2 CoPt 2 ordering, characterized by alternating single (001) layers of Co and pairs of (001) layers of Pt. The L1 0 struc- ture, observed experimentally through a wide range of compositions 53,54 , is predicted to be stable only in a very narrow chemical potential range as a result of the small difference between the slopes of the tie lines connecting L1 0 CoPt to Co 2 Pt and Co 2 Pt 3 . The experimentally observed L1 2 CoPt 3 ordering is entirely absent from the set of ground states, excluded by the depth of the common tangent between the CoPt 2 and FCC Pt phases.…”

Section: A Zero Kelvin and Finite Temperature Results For Pbementioning

confidence: 99%

Testing predictions from density functional theory at finite temperatures:β2-like ground states in Co-Pt

Decolvenaere¹,

Gordon²,

Ven³

2015

Phys. Rev. B

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We perform a critical assessment of the accuracy of DFT-based methods in predicting stable phases within the Co-Pt binary alloy. Statistical mechanical analysis applied to zero kelvin DFT predictions yields finite-temperature results that can be directly compared with experimental measurements. The predicted temperature-composition phase diagram is qualitatively incompatible with experimental observations, indicating that the predicted stability of long-period superstructures as ground states in the Co-Pt binary is incorrect. We also show that recently suggested methods to better align DFT and experiment via the hybrid functional HSE06 are unable to resolve the discrepancies in this system. Our results indicate a need for better verification of DFT based phase stability predictions, and highlight fundamental flaws in the ability of DFT to treat late 3d -5d binary alloys.

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“…where the lattice constants of bulk A1-Co50Pt50 (a A1-Co50Pt50 = 0.3809 nm) 22) , A3-Co80Pt20 (a A3-Co80Pt80 = 0.257 nm, c A3-Co80Pt80 = 0.4189 nm) 23) , and MgO (a MgO = 0.4211 nm) 24 26) , and CoFe/MgO 27) systems. The CoPt and the Co3Pt films prepared in the present study also seem to follow the growth mode.…”

Section: Resultsmentioning

confidence: 99%

Influence of Thickness on the Metastable Ordered Phase Formation in CoPt and Co3Pt Alloy Films

et al. 2015

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CoPt and Co3Pt alloy epitaxial films with the close-packed plane parallel to the surface are prepared on MgO(111) single-crystal substrates heated at 300 °C by varying the film thickness in a range between 2 and 40 nm. The structure is investigated from the viewpoints of the order degree and the atomic stacking sequence of close-packed plane. Metastable ordered phase formation is recognized for both CoPt and Co3Pt films. The CoPt and the Co3Pt films involve L11 and Bh(+D019) phases, respectively. Higher order degrees are recognized for thicker CoPt and Co3Pt films. As the thickness increases, the strain caused by accommodation of the lattice mismatch between film and substrate decreases. The ratios of out-of-plane to in-plane lattice spacings, 2dL1 1(222) / 2dL1 1(4 4 _ 0) and 2dB h(+D019)(0002) / 2dB h(+D019)(224 _ 0), of CoPt and Co3Pt films, respectively, decrease from 1.638 to 1.630 and from 1.637 to 1.616 with increasing the thickness from 2 to 40 nm. The films involving metastable phases show strong perpendicular magnetic anisotropies reflecting the magnetocrystalline anisotropies of L11 and Bh(+D019) crystals.

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Comparative investigation of structural and transport properties of L1₀NiPt and CoPt phases; the role of magnetism

Cited by 156 publications

References 30 publications

Ordering Process and Variant Selection under Magnetic Field in L10-type Co–50Pt and Fe–55Pd Alloys

Ordering Process and Variant Selection under Magnetic Field in L10-type Co–50Pt and Fe–55Pd Alloys

Testing predictions from density functional theory at finite temperatures:β2-like ground states in Co-Pt

Influence of Thickness on the Metastable Ordered Phase Formation in CoPt and Co3Pt Alloy Films

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Comparative investigation of structural and transport properties of L10NiPt and CoPt phases; the role of magnetism

Cited by 156 publications

References 30 publications

Ordering Process and Variant Selection under Magnetic Field in L10-type Co–50Pt and Fe–55Pd Alloys

Ordering Process and Variant Selection under Magnetic Field in L10-type Co–50Pt and Fe–55Pd Alloys

Testing predictions from density functional theory at finite temperatures:β2-like ground states in Co-Pt

Influence of Thickness on the Metastable Ordered Phase Formation in CoPt and Co3Pt Alloy Films

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Comparative investigation of structural and transport properties of L1₀NiPt and CoPt phases; the role of magnetism