Microstructural inhomogeneity and magnetic properties in Co-Cr sputtered films

Sagoi, Masayuki; Nishikawa, R.; Suzuki, Toshiyuki

doi:10.1109/tmag.1986.1064495

Cited by 33 publications

(7 citation statements)

References 4 publications

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“…Earlier work on Co–Cr thin films asserts that the deviations from the theoretical saturation moment arise due to existence of two nonmagnetic phases, specifically the hexagonal ε-Co phase and σ-CoCr phase which become stable at lower temperatures, which is consistent with our results and analysis.…”

Section: Resultssupporting

confidence: 92%

Phase Dynamics and Growth of Co₂Cr_1–xFe_xAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Omar

Dimitrakopoulou

Blum

et al. 2013

Crystal Growth & Design

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Many Heusler compounds are predicted to be half-metallic ferromagnets and thus find extensive interest as materials for spintronic applications, an example of which is the Co2Cr1–x Fe x Al series. So far, bulk samples of that series, in particular, Cr-rich samples, do not verify those predictions, and various studies have yielded results that are fraught with anomalies. Thin films as well do not meet expectations, neither in magnetoresistance ratio nor in degree of spin polarization and magnetic moments. Polycrystalline samples of Co2CrAl, Co2FeAl, and Co2Cr0.6Fe0.4Al were found to be phase segregated, a hurdle easily tackled by using the optical floating zone (FZ) technique. Hence, in this work, we have carried out crystal growth of Co2Cr1–x Fe x Al Heusler compounds, as a step toward understanding the intrinsic material properties of this series. Our results demonstrate that, although the phase segregation is eliminated in the FZ grown samples, an unexpected phase transformation via spinodal decomposition takes place in Cr-rich samples. This phase decomposition is found to strongly affect the magnetic properties and as well as other physical properties, e.g., spin polarization. Our finding presents new insight into the phase dynamics of this system and provides answers to many of the issues in this series of half-metallic ferromagnets.

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Section: Resultssupporting

confidence: 92%

Phase Dynamics and Growth of Co₂Cr_1–xFe_xAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Omar

Dimitrakopoulou

Blum

et al. 2013

Crystal Growth & Design

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“…Based on the present study, it appears that, at 750 °C in the phase diagram, we are still inside the twophase regime of the miscibility gap, as the extent of decomposition is increased due to annealing which is reflected in the relative intensities in XRD. Also, the saturation moment is further lowered which is understandable as the secondary σ-CoCr phase has been shown to have a strong effect on the magnetic properties in bulk [17] as well as in thin films [24]. After annealing at 1000 °C, the overall fraction of the secondary phase is less which is visible in the lower intensities for the tetragonal splitting of the main reflection as seen in Fig.4.…”

Section: Discussionmentioning

confidence: 91%

Effect of annealing on spinodally decomposed Co2CrAl grown via floating zone technique

Omar

Blum

Löser

et al. 2014

Journal of Crystal Growth

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Among the large class of Heusler compounds, Co 2 CrAl is predicted to be 100 % spin polarized and is hence, a potential candidate for application in spintronics. So far, the predicted properties have not been experimentally realized which may be attributed to the phase segregated nature of samples. This phase segregation is avoided using floating zone growth. However, the grown sample was found to have undergone phase transformation via spinodal decomposition at low temperatures. In the present work, thermal annealing has been done on the spinodally decomposed samples and its effect on microstructure, crystallographic structure and magnetic properties has been studied. Annealing experiments were done and analyzed in order to understand the extent of the solid state miscibility gap. With regards to the phase diagram, the two-phase regime was found to extend till 1000 °C. Even at 1250 °C, we are still inside the immiscibility region. The thermodynamic miscibility gap was thus found to exist until high temperatures and alternate routes might be required to obtain a single phase sample with the desired high spin polarization and Curie temperature in the Co-Cr-Al system.

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“…The degree of c-axis orientation and the diffraction intensity of the Co-Ni-Re-P alloy films are higher than those of Co-Ni-Re-Mn-P films in thinner regions. Therefore, a small change in c-axis orientation as a function of thickness produces almost no dependence of Hk on film thickness in the case of Co-Ni-Re-P film, because the Hk values are strongly dependent on the degree of c-axis orientation (20). On the other hand, perpendicular coercivity, H,.…”

Section: Discussionmentioning

confidence: 98%

The Structure of Electroless Cobalt Alloy Films for Perpendicular Magnetic Recording Media

Koiwa

Matsubara

Osaka

et al. 1986

J. Electrochem. Soc.

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Two types of electroless Co alloy films, Co40.1‐Ni44.2‐Re6.0‐P9.7 and Co23.6‐Ni58.5‐Re5.3‐Mn0.2‐P12.4 , were prepared for perpendicular magnetic recording media. The correlation between their structure and magnetic properties was investigated and discussed as a function of film thickness. The magnetic properties of these two types of films showed different patterns of dependence with respect to the film thickness. The Co‐Ni‐Re‐P alloy film gave a higher Hnormalcfalse(⊥false) (perpendicular coercivity) in regions where it was very thin; on the other hand, the Co‐Ni‐Re‐Mn‐P alloy film displayed a lower Hnormalcfalse(⊥false) at the initial film thickness. The composition was observed with AES measurements to be nearly independent of film thickness. The clear columnar structure of both types of films was confirmed by scanning electron microscopy (SEM) and especially by transmission electron microscopy (TEM) observations. Only the reflection high energy electron diffraction (RHEED) patterns for both types of film clearly showed different dependence patterns with respect to the film thickness. The Co‐Ni‐Re‐P film displayed a very highly c‐axis oriented structure even at the initial thin film stage. On the other hand, the Co‐Ni‐Re‐Mn‐P film showed a dependence of the degree of c‐axis orientation on the film thickness, which increased with film thickness. The differences in magnetic properties as a function of thickness were assumed to be due to the degrees of c‐axis orientation and change in magnetic domain structure.

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Microstructural inhomogeneity and magnetic properties in Co-Cr sputtered films

Cited by 33 publications

References 4 publications

Phase Dynamics and Growth of Co₂Cr_1–xFe_xAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Phase Dynamics and Growth of Co₂Cr_1–xFe_xAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Effect of annealing on spinodally decomposed Co2CrAl grown via floating zone technique

The Structure of Electroless Cobalt Alloy Films for Perpendicular Magnetic Recording Media

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Microstructural inhomogeneity and magnetic properties in Co-Cr sputtered films

Cited by 33 publications

References 4 publications

Phase Dynamics and Growth of Co2Cr1–xFexAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Phase Dynamics and Growth of Co2Cr1–xFexAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Effect of annealing on spinodally decomposed Co2CrAl grown via floating zone technique

The Structure of Electroless Cobalt Alloy Films for Perpendicular Magnetic Recording Media

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Phase Dynamics and Growth of Co₂Cr_1–xFe_xAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties

Phase Dynamics and Growth of Co₂Cr_1–xFe_xAl Heusler Compounds: A Key to Understand Their Anomalous Physical Properties