Giant reversible magnetocaloric effect in flower-like β-Co(OH)2 hierarchical superstructures self-assembled by nanosheets

Liu, Xianguo; Feng, Xiao; Or, Siu Wing; Sun, Yuping; Jin, Chuangui; Xia, Ailin

doi:10.1590/s1516-14392013005000171

Cited by 9 publications

(2 citation statements)

References 15 publications

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“…The MCE is the change in the entropy ΔS M of a material under an applied field H resulting in associated change in its temperature T. For this, ΔS M is written using the Maxwell equation given by [61][62][63][64][65][66][67][68]: Experimentally, it is easier to measure the isotherms M vs. H at fixed T and determine the area under the isotherm given by M H dH. In this case, equation ( 8) is replaced by All the isotherms in Co 2 RuO 4 were measured under the ZFC condition to access the virgin magnetic state.…”

Section: Temperature Dependence Of Magnetocaloric Effect (Mce)mentioning

confidence: 99%

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co₂RuO₄

Ghosh

Joshi

Pramanik

et al. 2020

J. Phys.: Condens. Matter

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Static and dynamic magnetic properties of normal spinel Co2RuO4 = (Co2+) are reported based on our investigations of the temperature (T), magnetic field (H) and frequency (f) dependence of the ac-magnetic susceptibilities and dc-magnetization (M) covering the temperature range T = 2 K–400 K and H up to 90 kOe. These investigations show that Co2RuO4 exhibits an antiferromagnetic (AFM) transition at TN ∼ 15.2 K, along with a spin-glass state at slightly lower temperature (TSG) near 14.2 K. It is argued that TN is mainly governed by the ordering of the spins of Co2+ ions occupying the A-site, whereas the exchange interaction between the Co2+ ions on the A-site and randomly distributed Ru3+ on the B-site triggers the spin-glass phase, Co3+ ions on the B-site being in the low-spin non-magnetic state. Analysis of measurements of M (H, T) for T < TN are used to construct the H–T phase diagram showing that TSG shifts to lower T varying as H2/3.2 expected for spin-glass state whereas TN is nearly H-independent. For T > TN, analysis of the paramagnetic susceptibility (χ) vs. T data are fit to the modified Curie–Weiss law, χ = χ0 + C/(T + θ), with χ0 = 0.0015 emu mol−1Oe−1 yielding θ = 53 K and C = 2.16 emu-K mol−1Oe−1, the later yielding an effective magnetic moment μeff = 4.16 μB comparable to the expected value of μeff = 4.24 μB per Co2RuO4. Using TN, θ and high temperature series for χ, dominant exchange constant J1/kB ∼ 6 K between the Co2+ on the A-sites is estimated. Analysis of the ac magnetic susceptibilities near TSG yields the dynamical critical exponent zν = 5.2 and microscopic spin relaxation time τ0 ∼ 1.16 × 10−10 sec characteristic of cluster spin-glasses and the observed time-dependence of M(t) is supportive of the spin-glass state. Large M–H loop asymmetry at low temperatures with giant exchange bias effect (HEB ∼ 1.8 kOe) and coercivity (HC ∼ 7 kOe) for a field cooled sample further support the mixed magnetic phase nature of this interesting spinel. The negative magnetocaloric effect observed below TN is interpreted to be due to the AFM and SG ordering. It is argued that the observed change from positive MCE (magnetocaloric effect) for T > TN to inverse MCE for T < TN observed in Co2RuO4 (and reported previously in other systems also) is related to the change in sign of (∂M/∂T) vs. T data.

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Section: Temperature Dependence Of Magnetocaloric Effect (Mce)mentioning

confidence: 99%

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co₂RuO₄

Ghosh

Joshi

Pramanik

et al. 2020

J. Phys.: Condens. Matter

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“…Hydrides emit H 2 gas [52][53][54][55]. A giant MCE was found in cobalt hydroxides Co(OH) 2 [212,259,280]. Ni-Mn-Ga alloys [169,213,253] contain expensive Ga. Mn-Fe-Ge [287], Mn-Ni-Ge [121] and Mn-Co-Ge [116,129,168,173,178,182] contain critical Ge [231]; these alloys can be doped with In [141], Si [159] and Fe [111,120,142]; Ge was successfully substituted by (Si,Al) [31].…”

Section: ∆S T T C (K) ∆T S (K)mentioning

confidence: 99%

Viable Materials with a Giant Magnetocaloric Effect

Zarkevich

Zverev

2020

Crystals

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This review of the current state of magnetocalorics is focused on materials exhibiting a giant magnetocaloric response near room temperature. To be economically viable for industrial applications and mass production, materials should have desired useful properties at a reasonable cost and should be safe for humans and the environment during manufacturing, handling, operational use, and after disposal. The discovery of novel materials is followed by a gradual improvement of properties by compositional adjustment and thermal or mechanical treatment. Consequently, with time, good materials become inferior to the best. There are several known classes of inexpensive materials with a giant magnetocaloric effect, and the search continues.

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Nature of magnetic interactions in β-Co(OH)₂ nanoparticles

Gupta

Tiwari

Kumar

2016

Phys. Status Solidi B

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Magnetic properties of β‐Co(OH)2 nanoparticles covering temperature range of 5–300 K in magnetic field upto 50 kG are studied. Zero‐field‐cooled and field‐cooled susceptibility as a function of temperature curves in different applied magnetic fields are seen to bifurcate at Tbf=11thinmathspacenormalK. Curie–Weiss fit of zero‐field‐cooled susceptibility curve well above Tbf yields θ=9thinmathspacenormalK and ionic magnetic moment μ=5.03thinmathspaceμB. Magnetization as a function of applied magnetic field curve below Tbf shows a two‐step transition to ferromagnetic state. Strength of three possible exchange interactions among Co2+ ions in β‐Co(OH)2 nanoparticles is also determined. We find that the present system orders antiferromagnetically at TN=11thinmathspacenormalK, with a dominant intralayer ferromagnetic coupling and a weaker interlayer antiferromagnetic coupling.

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Giant reversible magnetocaloric effect in flower-like β-Co(OH)2 hierarchical superstructures self-assembled by nanosheets

Cited by 9 publications

References 15 publications

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co₂RuO₄

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co₂RuO₄

Viable Materials with a Giant Magnetocaloric Effect

Nature of magnetic interactions in β-Co(OH)₂ nanoparticles

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Giant reversible magnetocaloric effect in flower-like β-Co(OH)2 hierarchical superstructures self-assembled by nanosheets

Cited by 9 publications

References 15 publications

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co2RuO4

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co2RuO4

Viable Materials with a Giant Magnetocaloric Effect

Nature of magnetic interactions in β-Co(OH)2 nanoparticles

Contact Info

Product

Resources

About

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co₂RuO₄

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co₂RuO₄

Nature of magnetic interactions in β-Co(OH)₂ nanoparticles