Exploration of room-temperature magnetocaloric effect in nanogranular Ni–Cr thin films

Alman, Vidya; Ramakrishna, V.; Battula, Sai Vittal; Sahu, Binod Bihari; Annadi, Anil; Singh, Vidyadhar; Bohra, Murtaza

doi:10.1557/s43579-023-00321-w

Cited by 5 publications

(5 citation statements)

References 17 publications

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“…NiCr alloys demonstrate a unique compositional dependence on T C , achieving values around room temperature with slight Cr doping, which render them suitable for MCE applications. [ 14 ] Recently, the coexistence of normal and inverse MCE in Ni 100‐x Cr x nanocrystalline thin films [ 15 ] with adjusting thickness and normal MCE in (Fe 70 Ni 30 ) 100−x Cr x nanoparticles [ 13 ] was reported. Inspired by these studies, we selected the interacting Ni 100‐x Cr x (0 ≤ x ≤ 15) DNS to investigate MCE properties using two different types of analytical models: the hyperbolic tangent and Gaussian‐distribution models.…”

Section: Introductionmentioning

confidence: 99%

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

Bohra,

Alman,

Khan

et al. 2024

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Determining the magnetocaloric effect (MCE) in dense nanoparticle systems (DNSs) poses a challenge due to the increased complexity of matter at the nanoscale. Given the interparticle magnetic interactions, diverse particle size and shape distributions, and the presence of inhomogeneous magnetic phases, selecting a suitable phenomenological model is essential to describe the temperature dependence of magnetic behavior in DNSs. Herein, we chose a cost‐effective Ni100‐xCrx DNS with adjustable magnetic transitions to showcase the resilience of the MCE across a broad temperature range (147–614 K). While the hyperbolic tangent model appears more fitting for materials with a single Curie temperature (TC), such as its parent bulk alloys, in the presence of a TC distribution a Gaussian distribution model proves to be better suited for DNSs. The latter model yields a magnetic entropy change, ΔSmax = 0.09–0.15 J kg‐K−1 in the DNS at a tiny field of 0.1T. The correlations between the broadening of the MCE peak and TC distribution are attributed to the particle size distribution and chemical inhomogeneity present in the DNS, paving the way for fine‐tuning MCE‐related properties such as the relative cooling power (13.17–33.45 J kg−1) and adiabatic temperature change (0.03–0.17 K). Our methodology not only enhances the potential for designing innovative MCE materials with broader operating ranges but also validates the universality of our phenomenological model for other families of nanocrystalline/nanogranular oxides/alloys thin films.

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Section: Introductionmentioning

confidence: 99%

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

Bohra,

Alman,

Khan

et al. 2024

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“…4,12 These properties can be recovered by protecting Cr segregation, adding more Cr doping, and optimizing the thicknesses of nanocrystalline films. Alloying Cr with Ni forms an excellent starting point to design materials for various room temperature applications, like tunable Curie temperature (T C ) substrates, 13 hyperthermia, 14 magnetocaloric, 15,16 and spintronics. 1,17,18 Often, polycrystalline Ni thin films form in FCC crystallinedisordered soft magnetic phases, which are characterized by inplane or out-of-plane anisotropy and a specific thickness range.…”

Section: ■ Introductionmentioning

confidence: 99%

“…This provides us only a preliminary guide; however, at the nanoscale, elemental demixing, and surface segregation of Cr are major hurdles to getting desired magnetic properties. , These properties can be recovered by protecting Cr segregation, adding more Cr doping, and optimizing the thicknesses of nanocrystalline films. Alloying Cr with Ni forms an excellent starting point to design materials for various room temperature applications, like tunable Curie temperature ( T C ) substrates, hyperthermia, magnetocaloric, , and spintronics. ,, …”

Section: Introductionmentioning

confidence: 99%

Thickness-Driven Magnetic Behavior in Ni–Cr Nanocrystalline Thin Films: Implications for Spintronics and Magnetic Cooling

Alman

Annadi

Murapaka

et al. 2023

ACS Appl. Nano Mater.

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Alloying antiferromagnetic Cr with ferromagnetic Ni forms an excellent starting point to design materials for various room temperature applications, such as spintronics, the magnetocaloric effect, and hyperthermia, thanks to its tunable Curie temperature, T C , and competing magnetic interactions. In this report, we present a comprehensive analysis of the relationships among film thickness, Cr surface segregation, and magnetic properties in nanocrystalline Ni 100−x Cr x (x = 5−15 at. %) thin films. We assess the impact of Cr segregation evolution on various magnetic transitions as the thickness and Cr doping level increase. These films exhibited ferromagnetic to paramagnetic transitions at higher temperatures and ferromagnetic to spin-glass transitions at low temperatures, which resulted in a phase diagram that differed from the bulk equilibrium phase diagram. Further, magnetometry and magnetic force microscopy were performed to investigate the magnetic anisotropy and magnetic domain structure as a function of film thickness. It is found that the perpendicular component of magnetic anisotropyled to a stripe domain structure in films with critical thicknesses above 20 nm. Substantial changes in the magnetization behavior of nanocrystalline Ni 100−x Cr x thin films within a few Cr at. % doping provide a means for adjusting both soft and hard magnetic component applications.

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“…However, the higher cost, toxicity, and scarcity of R elements limit the available choices, and researchers are looking for T metals -based soft ferromagnetic compounds without R elements that work at elevated temperatures [13][14][15][16][17]. MCE effects have been reported in metallic ternary nanoalloys [(Fe 70 Ni 30 ) 100−x Cr x (x = 0, 1, 3, 5, 6, and 7); -S max D = 0.27-0.38 J kg −1 K −1 (1 T) and 1.11-1.58 J kg −1 K −1 (5 T), T C = 215-438 K] [13] and binary bulk alloy…”

Section: Introductionmentioning

confidence: 99%

“…% Cr, with the 5 at. % Cr being notable for its Tc around room temperature [15,18,19], holding promise for MCE applications. Our recent study demonstrates that the thickness variation of these Ni 100−x Cr x layers is a second lever of action that enables external tuning competence of the soft magnetic properties (T C , saturation magnetization, M S , and coercive field H C ) by inducing Cr-surface segregation [18], which can eventually be used to create various magnetic ground states for MCE and IMCE functionalities.…”

Section: Introductionmentioning

confidence: 99%

Coexistence of normal and inverse magnetocaloric effect in inhomogeneous Ni₉₅Cr₅ layers

et al. 2023

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Understanding of the coexistence of normal and inverse magnetocaloric effects (MCE) makes it promising for use in magnetic cooling applications. This study discusses the selection of Ni95Cr5 layers and their expected magnetocaloric effects for an extended temperature range (200 - 800 K). These layers offer a wide range of suitable magnetic ordering temperatures as a function of thicknesses. A modified phenomenological model was used to estimate the entropy changes (∆SM) at non-cryogenic and cryogenic ordering temperatures. The ΔS values increase somewhat with increasing thickness due to enhanced magnetization values. Under adiabatic magnetic field variation, normal and inverse MCE are computed near the ferromagnetic-paramagnetic and spin glass transition temperatures, respectively. Based on their ∆Smax values (= -0.06 to 0.11 J/kg-K) and relative cooling power (RCP = 7.6 to 15.5 J/kg) at the smallest magnetic field of 0.5 kOe, which are comparable to other MCE layer materials. The current study demonstrates that adjusting thickness, in addition to Cr doping, can externally regulate soft magnetic and magnetocaloric properties to create diverse magnetic ground states for future MCE and inverse MCE functionalities.

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Exploration of room-temperature magnetocaloric effect in nanogranular Ni–Cr thin films

Cited by 5 publications

References 17 publications

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

Thickness-Driven Magnetic Behavior in Ni–Cr Nanocrystalline Thin Films: Implications for Spintronics and Magnetic Cooling

Coexistence of normal and inverse magnetocaloric effect in inhomogeneous Ni₉₅Cr₅ layers

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Exploration of room-temperature magnetocaloric effect in nanogranular Ni–Cr thin films

Cited by 5 publications

References 17 publications

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

Thickness-Driven Magnetic Behavior in Ni–Cr Nanocrystalline Thin Films: Implications for Spintronics and Magnetic Cooling

Coexistence of normal and inverse magnetocaloric effect in inhomogeneous Ni95Cr5 layers

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Coexistence of normal and inverse magnetocaloric effect in inhomogeneous Ni₉₅Cr₅ layers