Magnetic irreversibility, spin-wave excitations and magnetocaloric effect in nanocrystalline Gadolinium

Mathew, S. P.; Kaul, S. N.; Nigam, A. K.; Probst, Anne-Catherine; Birringer, R.

doi:10.1088/1742-6596/200/7/072047

Cited by 20 publications

(25 citation statements)

References 7 publications

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“…However, magnetic properties of materials in a thin film state may differ from properties of the bulk materials due to both the finite size effect 3 and the change of the crystalline structure 4, 5. Moreover, it was recently shown that an MCE in bulk nanocrystalline Gd differs from one in bulk coarse‐grained Gd 6. But in RE thin films, a grain size is generally of order of a few nanometres 5.…”

Section: Introductionsupporting

confidence: 89%

Structure and magnetic properties of nanostructured GdTb thin films

Svalov

Vas’kovskiy

Barandiarán

et al. 2011

Physica Status Solidi (a)

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Various series of Gd100−xTbx films and multilayers with a different thickness of rare earth (RE) layers were prepared by rf‐sputtering. The increase of Gd content leads to an increase of the magnetic ordering temperature (Tord). At the same time substitution of the low anisotropic gadolinium by high anisotropic terbium causes an increase of the coercivity of the samples. The decrease of the RE layer thickness (LRE) results in the change of the RE films structure: the crystalline grain size goes down and for LRE < 3 nm an amorphous phase appears. For LRE < 5 nm all compositions show a significant decrease of the ordering temperature. In contrast with bulk Gd100−xTbx alloys, in case of thin films, the value of Tord can be tailored, not only by the change of the composition, but also by the variation of the thickness of Gd100−xTbx films.

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Section: Introductionsupporting

confidence: 89%

Structure and magnetic properties of nanostructured GdTb thin films

Svalov

Vas’kovskiy

Barandiarán

et al. 2011

Physica Status Solidi (a)

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“…18 The reduction of the macroscopic magnetization in the nanocrystalline material at magnetic fields up to 9 T and low temperature and, in particular, its variation according to M/M ∝ D −1 indicate the special role of the grain boundaries as a dominant source of spin disorder since this scaling law is characteristic for the volume fraction of atoms located in the core regions of grain boundaries. The notion of grain-boundary-induced spin disorder is supported by recent experimental 51 and theoretical 52 studies.…”

Section: B Magnetometrymentioning

confidence: 94%

Neutron scattering study of the magnetic microstructure of nanocrystalline gadolinium

et al. 2012

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We report grain-size-dependent results on nanocrystalline bulk Gd obtained by magnetic small-angle neutron scattering (SANS) and magnetometry. This approach allows one to study systematically how the magnetic microstructure of this rare-earth metal is affected by defects in the atomic microstructure, which are largely present in nanocrystalline materials, predominantly in the form of grain boundaries. The neutron scattering data reveal two types of angular anisotropies in the magnetic-field-dependent scattering cross section that are typically not seen in the coarse-grained polycrystal. In particular, a cloverleaf-shaped anisotropy and an elongation of the scattering pattern in the direction of the applied magnetic field have been detected. While the first result, which is an exceptional finding even in the nanocrystalline state, can be attributed to pronounced spin disorder in the vicinity of the Gd grain boundaries, the second anisotropy is related to spin misalignment due to the random magnetocrystalline anisotropy within the individual crystallites. Furthermore, we have calculated the correlation function of the spin misalignment from the radially averaged data, which gives access to the characteristic length scales on which the magnetization is perturbed by crystal defects. The results of this real-space analysis independently support the findings from magnetometry and field-dependent SANS. Wide-angle x-ray diffraction data indicate that stacking faults may limit the range of spin-misalignment fluctuations due to random anisotropy in this material.

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“…Its magnetic characterization has unveiled significant irreversibility which was attributed to intra-and interfacial anisotropies which hinder the complete alignment of the magnetic moments (saturation) and consequently significantly diminishes (in comparison to bulk) the magnetic entropy change even for fields as high as 50 kOe. 45 Using a similar method, Aruna and coworkers have produced single Gd particles. To minimize further the oxygen content in the chamber, prior to deposition, a small amount of Gd was evaporated onto the shutters to serve as getter.…”

Section: Magnetocaloric Systemsmentioning

confidence: 99%