Metamagnetic transition and reversible magnetocaloric effect in antiferromagnetic DyNiGa compound

Rare-earth(R)-based materials with large reversible magnetocaloric effect(MCE)are attracting much attention as the promising candidates for low temperature magnetic refrigeration.In the present work,the magnetic properties and MCE of DyNiGa compound with TiNiSi-type orthorhombic structure are studied systematically.The DyNiGa undergoes a magnetic transition from antiferromagnetic(AFM)to paramagnetic state with Néel temperature TN=17 K.Meanwhile,it does not show thermal and magnetic hysteresis,revealing the perfect thermal and magnetic reversibility.Moreover,the AFM state can be induced into a ferromagnetic state by a relatively low field,and thus leading to a large reversible MCE,e.g.,a maximum magnetic entropy change(-ΔSM)of 10 J/kg·K is obtained at 18 K under a magnetic field change of 5 T.Consequently,the large MCE without thermal or magnetic hysteresis makes the DyNiGa a competitive candidate for magnetic refrigeration of hydrogen liquefaction.

Effects of dipolar interactions on the magnetic hyperthermia of Zn_(0.3)Fe_(2.7)O_(4) nanoparticles with different sizes

Tumor-targeted magnetic hyperthermia has recently attracted much attention.Magnetic nanoparticles(NPs) are heat mediator nanoprobes in magnetic hyperthermia for cancer treatment.In this paper,single cubic spinel structural Zn_(0.3)Fe_(2.7)O_(4) magnetic NPs with sizes of 14 nm-20 nm were synthesized,followed by coating with SiO_(2) shell.The SLP value of Zn_(0.3)Fe_(2.7)O_(4)/SiO_(2) NPs below 20 nm changes non-monotonically with the concentration of solution under the alternating current(AC) magnetic field of 430 kHz and 27 kA/m.SLP values of all Zn_(0.3)Fe_(2.7)O_(4)/SiO_(2) NPs appear a peak value with change of solution concentration.The solution concentrations with optimal SLP value decrease with increasing magnetic core size.This work can give guidance to the better prediction and control of the magnetic hyperthermia performance of materials in clinical applications.

Table-Like Large Magnetocaloric Effect in the Misch Metal RSi Compound

Magnetic properties and the magnetocaloric effect(MCE)of the RSi(R=Ce,Pr,Nd)compounds made of Misch metal(MM)are investigated.Two transitions are found at 12K and 38K.Field variation generated large MCE and two peaks are found in the magnetic entropy change(△S)curves,which correspond to the two transition temperatures.The maximum values of the magnetic entropy changes(△S)are found to be-5.1 J/(kg·K)and-9.3 J/(kg·K)for the field ranges of 0-2 T and 0-5 T,respectively.The large AS as well as ultra-low price of MM make(MM)Si a competitive magnetic refrigerant candidate for low temperature in Eriksson cycle.

Effect of Magnetic Anisotropy on Magnetic Thermal Induction of Mn_(0.3)Zn_(0.3)Co_xFe_(2.4-x)O_4 Nanoparticles

Mn_(0.3)Zn_(0.3)Co_xFe_(2.4-x)O_4 series magnetic nanoparticles are prepared by the high-temperature organic solvent method, and Mn_(0.3)Zn_(0.3)Co_xFe_(2.4-x)O_4@SiO_2 composite nanoparticles are prepared by the reverse microemulsion method. The as-prepared samples are characterized, and the results show that the magnetic anisotropy constant of nanoparticles increases with the cobalt content, and the magnetic thermal induction shows a trend of increasing first and then decreasing. The optimal magnetic thermal induction is obtained at x = 0.12 with a specific loss power of 2086 w/gmetal, which is a bright prospect in clinical magnetic hyperthermia.

Spontaneous magnetization and magnetic domain texture of strontium hexaferrite in equilibrium state

The spontaneous magnetization and equilibrium domain of SrFeOunder zero external field by micromagnetic simulation and experimental measurements were investigated.It was found that the magnetic moment distribution was extremely sensitive to the grain size of strontium hexaferrite.The critical diameter from single-domain to multi-domain can be controlled by changing the thickness and diameter,which is the key to improve the permanent magnet properties.