Details

Autor(en) / Beteiligte

• Nguyet, Dao Thi Thuy
• Duong, Nguyen Phuc
• Satoh, Takuya
• Anh, Luong Ngoc
• Hien, Than Duc

Titel

Magnetization and coercivity of nanocrystalline gadolinium iron garnet

Ist Teil von

• Journal of magnetism and magnetic materials, 2013-04, Vol.332, p.180-185

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2013

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Gadolinium iron garnet (GdIG) nanoparticles with mean particle size of about 37nm have been synthesized by citrate precursor gel formation followed by annealing at 800°C for 2 hours. Magnetic behavior of clustered GdIG nanoparticles was studied in temperature range from 5K to above Curie temperature. The sample shows a magnetization compensation temperature Tcomp∼286.5K and a Curie temperature TC∼560K. In comparison with the bulk saturation magnetization, the sample exhibits lower spontaneous magnetization in the temperature region from 5K to Tcomp whereas higher spontaneous magnetization is observed at higher temperatures up to near the Curie point. The magnetization curves show a differential susceptibility in high fields which increases sharply below 50K. At very low temperatures, irreversibility was observed in the magnetization loops, enduring in the fields up to ∼12.5kOe. The spontaneous magnetization, high-field susceptibility and low-temperature irreversible effect were discussed based on a model for the interacting particles consisting of ferrimagnetically aligned core spins and disordered spins in surface layer which become frozen at low temperatures. We proposed a mechanism for the enhancement of the spontaneous magnetization above Tcomp in which the Gd and Fe spins in the surface layer are largely decoupled at high temperatures and the surface Fe spins realign to the magnetic moment of the core. The magnetic coercivity Hc at low temperatures is governed by the effective anisotropy whereas in the vicinity of the compensation point a peak in the coercive force shows up as a result of the so-called paraprocess with the maximum value of 1.2kOe at Tcomp and by further increasing temperature the coercivity decreases and eventually vanishes at about 500K. The interparticle interactions were found to play an important role in the hysteresis behavior of the sample. ► Gd3Fe5O12 nanoparticles with mean particle size ∼37nm were prepared by sol-gel method. ► Magnetization process was investigated in temperature range 5–600K. ► Maximum coercivity attains 1.2kOe at compensation temperature. ► Anomalous magnetic behaviors were discussed based on core−shell model. ► Interparticle interactions affect hysteresis curves at high temperatures.