Magnetocaloric properties of nanocrystalline La0.125_{0.125}Ca0.875_{0.875}MnO3_{3}

Some recent experimental studies show the invisibility of antiferromagnetic transition in the cases of manganites when their particle size is reduced to nanometer scale. In complete contrast to these cases, we have observed the signature of antiferromagnetic transition in the magnetocaloric properties of nanocrystalline La$_{0.125}$Ca$_{0.875}$MnO$_{3}$ of average particle size 70 and 60 nm similar to its polycrystalline bulk form. The system exhibit inverse magnetocaloric effect in its polycrystalline and nanocrystalline form. An extra ferromagnetic phase is stabilized at low temperature for the sample with particle size $\sim 60$ nm.Comment: 3 Figure

Modification of the Charge ordering in Pr1/2_{1/2}Sr1/2_{1/2}MnO3_{3} Nanoparticles

Transport and magnetic properties have been studied in two sets of sol-gel prepared Pr$_{1/2}$Sr$_{1/2}$MnO$_{3}$ nanoparticles having average particle size of 30 nm and 45 nm. Our measurements suggest that the formation of charge ordered state is largely affected due to lowering of particle size, but the ferromagnetic transition temperature ($T_{C}$) remains unaffected.Comment: Accepted in J. Appl. Phy

Follicular Dendritic Cell Sarcoma of the Neck Recurring after Trimodality Therapy: A Rare and Aggressive Neoplasm

Follicular dendritic cell sarcoma is one of the rare and aggressive neoplasms originating from follicular dendritic cells of lymphoid tissues. It commonly presents as asymptomatic lymphadenopathy, but extranodal involvement such as oral cavity, mediastinum, liver, and spleen are also reported. The disease often has an indolent course. Current knowledge on its pathogenesis is limited and due to its rarity, follicular dendritic cell sarcoma has no definite treatment strategy at present. Here we report a case of a 24-year old male with follicular dendritic cell sarcoma of neck, treated with wide local excision, post operative radiation and chemotherapy, and developing pulmonary metastasis after a disease-free period of 15 months

Managing hysteresis of Gd5Si2Ge2 by magnetic field cycling

The influence of magnetic field cycling through the first-order magnetostructural transformation on the magnetic and magnetocaloric properties, as well as hysteresis of polycrystalline Gd5Si2Ge2, has been studied using magnetometry. The cycling has a minimal effect on the magnetic field-induced entropy change and the phase transformation temperature of the material. On the other hand, magnetic hysteresis decreases by 30% after approximately ten cycles and remains low unless the sample is moved far into the paramagnetic regime. Factors playing a role in the history dependence of hysteresis have been discussed

Impact of structural disorder on the magnetic ordering and magnetocaloric response of amorphous Gd-based microwires.

We have studied the impact of structural disorder on the magnetic ordering and magnetocaloric response of amorphous Gd 68 Ni 32 and Gd 53 Al 24 Co 20 Zr 3 microwires. We find that the presence of structural disorder significantly broadens the paramagnetic to ferromagnetic (PM-FM) transition and the temperature-dependent magnetic entropy change, while the nature of the second-order magnetic transition and long-range ferromagnetic order are not essentially affected by this effect. The large magnetic moment of Gd and the presence of the long-range ferromagnetic order are believed to result in a large magnetic entropy change, which together with the broadening of the PM-FM transition due to structural disorder contribute to a large refrigerant capacity. The excellent magnetocaloric properties of the amorphous microwires make them very promising candidates for active magnetic refrigeration

Enhanced cryogenic magnetocaloric effect in Eu8Ga16Ge30 clathrate nanocrystals

We observe an enhanced magnetic entropy change ( D S M ) at cryogenic temperatures (T < 20 K) in Eu 8 Ga 16 Ge 30 clathrate (type-I) nanocrystals prepared by a ball milling method. With reduction in the crystal size to 15 nm, D S M is enhanced at low temperatures, reaching the highest value ( 10 J/kg K) at 5 K for a field change of 5 T. For all samples investigated, there is a cross-over tem- perature ( 25 K) in D S M (T) above which D S M decreases with crystal size, opposite to that observed at low temperatures. A careful analysis of the magnetic and magnetocaloric data reveals that as the crystal size decreases the magnetic interaction between Eu 2 þ ions on the Eu2 site gov- erning the primary ferromagnetic transition at 35 K becomes gradually weaker, in effect, altering the interaction between Eu 2 þ ions occupying the Eu1 and Eu2 sites responsible for the secondary ferromagnetic transition at 15 K. As a result, we have observed a strong change in magnetization and the enhancement of D S M at low temperature

Magnetic structure of selected Gd intermetallic alloys from first principles

Using first-principles calculations, based on disordered local moment (DLM) theory combined with the self-interaction corrected local spin density approximation (SIC-LSDA), we study magnetic correlations in the paramagnetic state of GdX(X=Cu, Zn, Ga, Ag, Cd, In, Au, Hg, and Tl) intermetallics and their alloys. The predicted magnetic orders and ordering temperatures that these correlations lead to are in overall good agreement with available experiments. The interactions between the Gd f-electron local moments are mediated by the valence electrons of the intermetallics which comprise both Gd and Xd bands as well as sp bands. There are RKKY-like features such as dependence on the number of sp-valence electrons but other variations manifest themselves in the phase diagrams as regions of incommensurate magnetic ordering, the origin and range of which are related to the binding energies of the alloying anion d states, and their propensity to hybridize with the Gd states at the Fermi level

Giant enhancement of the magnetocaloric response in Ni-Co-Mn-Ti by rapid solidification

Magnetocaloric refrigeration is a solid-state cooling approach that promises high energy efficiency and low environmental impact. It remains uncompetitive with conventional vapor-compression technologies due to lack of high-performing materials that exhibit large magnetocaloric effects in low magnetic fields. Here we report a game-changing enhancement of the magnetocaloric response in a transition-metal-based Ni-Co-Mn-Ti. Mechanically and chemically stable rapidly solidified ribbons exhibit magnetic entropy changes as high as ~27 J⋅kg-1K-1 for a moderate field change of 2 T, comparable to or larger than the best known materials for near-room temperature applications. The ribbons can be easily manufactured in large quantities and the transition temperature can be adjusted by varying Co concentration