Tunable magnetocaloric effect in La0.7Ca0.3MnO3 nanoparticles

2018 ◽  
Vol 32 (26) ◽  
pp. 1850290
Author(s):  
S. Qaseem ◽  
M. Naeem ◽  
S. Rizwan Ali
Keyword(s):  
Particle Size ◽  
Magnetocaloric Effect ◽  
Magnetic Transition ◽  
Second Order ◽  
Gradual Transition ◽  
Cooling Power ◽  
Zero Field ◽  
Colossal Magnetoresistive ◽  
Three Samples ◽  
Saturation Region

We study ferromagnetic to paramagnetic transition using Banerjee criterion in colossal magnetoresistive La[Formula: see text]Ca[Formula: see text]MnO3 nanoparticles of different sizes (20, 26 and 32 nm). These particles are chemically prepared by a modified citrate route. Particle sizes are estimated by X-ray diffraction (XRD). Sample morphology and size distribution are examined by a transmission electron microscope. Order of transition is determined by measuring magnetic field dependence of magnetization near Curie temperature T[Formula: see text]. Our results reveal second-order magnetic transition in all three different-sized particles in contrast to the first-order transition reported in bulk samples. This is further supported by temperature dependences of zero-field-cooled (ZFC) and field-cooled (FC) magnetizations. FC curves show gradual transition for all three samples without any saturation region as is the case of bulk. T[Formula: see text] is extracted from ZFC curves and is found to be 240 K for 20 nm particles and 258 K for both 26 and 32 nm particles. Magnetocaloric effect as a function of particle size also confirms the second-order magnetic transition in all three samples. The relative cooling power at 20 kOe is found to be decreasing with decreasing particle size.

scholarly journals Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Rongrong Wu ◽  
Feiran Shen ◽  
Fengxia Hu ◽  
Jing Wang ◽  
Lifu Bao ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetocaloric Effect ◽  
Magnetic Transition ◽  
Magnetic Hysteresis ◽  
Negative Thermal Expansion ◽  
Entropy Change ◽  
Cooling Power ◽  
Austenitic Phase ◽  
Magnetic Actuators ◽  
Practical Applications

Abstract Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RC effe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials.

Large Magnetization and Reversible Magnetocaloric Effect at the Second-Order Magnetic Transition in Heusler Materials

2016 ◽  
Vol 28 (17) ◽  
pp. 3321-3325 ◽  
Author(s):  
Sanjay Singh ◽  
Luana Caron ◽  
Sunil Wilfred D'Souza ◽  
Tina Fichtner ◽  
Giacomo Porcari ◽  
...  
Keyword(s):  
Magnetocaloric Effect ◽  
Magnetic Transition ◽  
Second Order

scholarly journals Tuning magnetic and magnetocaloric properties of Pr0.6Sr0.4MnO3 through size modifications

2021 ◽  
Author(s):  
Anita D Souza ◽  
Megha Vagadia ◽  
Mamatha Daivajna
Keyword(s):  
Particle Size ◽  
Magnetic Transition ◽  
Entropy Change ◽  
Cooling Power ◽  
Magnetic Transition Temperature ◽  
Temperature Range ◽  
Spin Disorder ◽  
Magnetocaloric Properties ◽  
Surface Disorder ◽  
Enhanced Surface

AbstractParticle size as an effective tool for controlling the magnetic and magnetocaloric properties of Pr0.6Sr0.4MnO3 samples has been studied. In the present work, a direct influence of particle size on the magnitude of magnetization and magnetic transition temperature, TC, can be seen. The TC drops from 309 to 242 K, while the saturation magnetization (MS) decreases from 3.6 to 0.5 μB/f.u. as the particle changes from 120 to 9 nm. Concurrently, coercivity (HC) exhibits a drastic rise emphasizing the enhanced surface disorder in the nanoparticles. Another interesting observation is in the magnetic entropy change, ΔS, which though decreases in magnitude from 5.51 to 3.90 J/Kg-K as particle size decreases from 120 to 30 nm, but the temperature range of ΔS (i.e., relative cooling power, RCP) increases from 184.33 to 228.85 J/Kg. Such interplay between magnitude and wider temperature range of ΔS, which can be fine-tuned by particle size, provides an interesting tool for using surface spin disorder, as a control mechanism in modifying physical properties.

scholarly journals Complex magnetic properties associated with competing local and itinerant magnetism in $${\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mily Kundu ◽  
Santanu Pakhira ◽  
Renu Choudhary ◽  
Durga Paudyal ◽  
N. Lakshminarasimhan ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Neutron Diffraction ◽  
Single Phase ◽  
Magnetic Transition ◽  
Muon Spin Rotation ◽  
Antiferromagnetic Coupling ◽  
Diffraction Measurement ◽  
Zero Field ◽  
Crystalline Electric Field ◽  
X Ray

AbstractTernary intermetallic compound $${\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}$$ Pr 2 Co 0.86 Si 2.88 has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ($$\mu$$ μ SR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below $$\sim$$ ∼ 4 K. Neutron diffraction measurement further reveals that the magnetic ordering is antiferromagnetic in nature with an weak ordered moment. The high temperature magnetic phase has been attributed to glassy in nature consisting of ferromagnetic clusters of itinerant (3d) Co moments as evident by the development of internal field in zero-field $$\mu$$ μ SR below 50 K. The density-functional theory (DFT) calculations suggest that the low temperature magnetic transition is associated with antiferromagnetic coupling between Pr 4f and Co 3d spins. Pr moments show spin fluctuation along with unconventional orbital moment quenching due to crystal field. The evolution of the symmetry and the crystalline electric field environment of Pr-ions are also studied and compared theoretically between the elemental Pr and when it is coupled with other elements such as Co. The localized moment of Pr 4f and itinerant moment of Co 3d compete with each other below $$\sim$$ ∼ 20 K resulting in an unusual temperature dependence of magnetic coercivity in the system.

scholarly journals Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

2021 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Luis M. Moreno-Ramírez ◽  
Victorino Franco
Keyword(s):  
Magnetic Field ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Second Order ◽  
Zero Field ◽  
First Order ◽  
Magnetic Field Change ◽  
Magnetocaloric Materials ◽  
Moderate Magnetic Field ◽  
The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

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