Keywords : magnetic materials

Hydrothermal synthesis and electrochemical properties of MnFe2O4 nanoplates

Hanfeng Liang; Xun Xu; Jinqing Hong; Zhoucheng Wang

Advanced Materials Letters, 2017, Volume 8, Issue 11, Pages 1052-1056
DOI: 10.5185/amlett.2017.1543

MnFe2O4 nanoplates have been synthesized by a simple hydrothermal method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) have been employed to characterize the structure and morphology of the as-prepared sample. The results show that the products are plate-like morphology with 100-500 nm in length and 100-200 nm in thickness. Contrast experiments indicate that the formation of the plate-like nanostructure could be ascribed to the effect of citrate complexation. Magnetic measurements at 300 K gave the saturation magnetization and the coercive field of nanoplates 39.2 emu g -1 and 91.5 Oe, respectively. The electrochemical performance as anode material for lithium-ion batteries was further evaluated by cyclic voltammetry (CV), electrochemical impedance and charge-discharge measurements. It was demonstrated that the material could provide an initial reversible capacity of 1067 mAh g -1 at a current density of 0.1 mA cm -2 over the voltage range from 0.5 to 3.0 V. 

Effect of heat treatment on the structure and magnetic properties of Sm-Fe alloys obtained by mechanical alloying

Nikolay G. Razumov; Aleksandr S. Verevkin; Anatoly A. Popovich

Advanced Materials Letters, 2017, Volume 8, Issue 5, Pages 673-677
DOI: 10.5185/amlett.2017.7071

The effect of heat treatment on the structure and magnetic properties of Sm-Fe alloys obtained by mechanical alloying was investigated. The crystallization temperature of Sm2Fe17, an amorphous alloy obtained by mechanical alloying, was determined using differential scanning calorimetry. Based on these results, various samples were annealed at different isothermal holding temperatures, and those with the best magnetic properties were found. Experimental studies show that decreasing the isothermal holding temperature from 750 °C to 630 °C increases magnetic characteristics nearly four times. The saturation magnetization, romance and coercivity of the Sm2Fe17 powder were 121 emu/g, 28.5 emu/g and 800 Oe, respectively. 

Structure Dependent Room Temperature Ferromagnetism In Co, Nb Co-doped BaTiO3 Thin Films Prepared By RF Sputtering

R. Siddheswaran; Petr Nov

Advanced Materials Letters, 2016, Volume 7, Issue 6, Pages 445-448
DOI: 10.5185/amlett.2016.6183

Thin films of BaTiO3 and Co, Nb co-doped BaTiO3 on glass and Si (100) substrates were deposited by RF sputtering (at 350 ºC), and annealed. The amorphous and crystalline phases were observed for the as-deposited and annealed samples, respectively from the X-ray diffraction (XRD) studies. The magnetic behaviour of the pure and doped BaTiO3 films was studied by vibrating sample magnetometry (VSM). In this study, the ferromagnetic behaviour at room temperature was observed in the Co, Nb co-doped BaTiO3 of both amorphous and crystalline films. The annealed polycrystalline Co, Nb co-doped BaTiO3 films have the larger saturation magnetization and coercivity than the amorphous films. The room temperature ferromagnetic responses were also observed by the Magneto-optical Kerr effect (MOKE) measurements for both as-deposited and annealed samples. 

Effect Of Grain Size On The Structural And Magnetic Properties Of Nanocrystalline Al3Fe5O12 By Aqueous Coprecipitation Method

S.E.Naina Vinodini

Advanced Materials Letters, 2015, Volume 6, Issue 8, Pages 717-725
DOI: 10.5185/amlett.2015.5874

Al3Fe5O12 (AIG) nanopowders were synthesized at different pH using aqueous co-precipitation method. The effect of pH on the phase formation of AIG is characterized using XRD, TEM, FTIR and TG/DTA. From the Scherer formula, the particle sizes of the powders were found to be 15, 21, 25 and 30 nm for pH= 9, 10, 11 and 12, respectively. It is found that as the pH of the solution increase the particle size also increases. It is clear from the TG/DTA curves that as the pH is increasing the weight losses were found to be small. The nanopowders were sintered at 900°C/4hrs using conventional sintering method. The phase formation is completed at 800°C/4h which is correlated with TG/DTA. The average grain size of the samples is found to be ~55 nm. As the pH increases the magnetization values are also increasing. The saturation magnetization was found to be 4 emu/g, 6 emu/g, 7 emu/g and 9 emu/g corresponding to pH= 9, 10, 11 and 12, respectively which clearly shows that the magnetization values are dependent on pH. Room temperature magnetization measurements established these compounds to be soft magnetic.  The dielectric and magnetic properties (εʹ, εʺ, µÊ¹ and µÊº) of AIG was studied over a wide range of frequency (1GHz-50GHz). With increase of pH both εʹ and µÊ¹ increased. This finding provides a new route for AIG materials that can be used in the gigahertz range.

Liquid-Phase Synthesis of Nickel Nanoparticles stabilized by PVP and study of their structural and magnetic properties

Mandeep Singh; Manish Kumar; Frantisek Stipanek; Pavel Ulbrich; Pavel Svoboda; Eva Santava; M.L. Singla

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 409-414
DOI: 10.5185/amlett.2011.4257

We have synthesized nickel nanoparticles using nickel chloride as a precursor in ethanol using PVP (Poly Vinyl Pyrrolidone) as a surfactant and hydrazine hydrate as reducing agent at 60 °C in a facile manner. The structural analysis showed that particles are face-centered cubic and monodisperse within the PVP matrix with average size about 3 nm. The magnetic analysis shows the superparamagnetism of the single-domain nickel nanoparticles with the blocking temperature (Tb) exists around 14 K with clear hysteretic effect observation below this blocking temperature.