Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures
In this work MnxCo1−xFe2O4 nanoparticles (NPs) were synthesized using a chemical co-precipitation method. Phase purity and structural analyses of synthesized NPs were performed by X-ray diffractometer (XRD). Transmission electron microscopy (TEM) reveals the presence of highly crystalline and narrowly-dispersed NPs with average diameter of 14 nm. The Fourier transform infrared (FTIR) spectrum was measured in the range of 400–4000 cm−1 which confirmed the formation of vibrational frequency bands associated with the entire spinel structure. Temperature-dependent magnetic properties in anti-ferromagnet (AFM) and ferromagnet (FM) structure were investigated with the aid of a physical property measurement system (PPMS). It was observed that magnetic interactions between the AFM (Mn) and FM (CoFe2O4) material arise below the Neel temperature of the dopant. Furthermore, hysteresis response was clearly pronounced for the enhancement in magnetic parameters by varying temperature towards absolute zero. It is shown that magnetic properties have been tuned as a function of temperature and an externally-applied field.
Ionic disorder and Yaffet–Kittel angle in nanoparticles of ZnFe2O4 prepared by sol‐gel method
ZnFe2O4 nanoparticles have been prepared by sol‐gel methods. Mössbauer spectra from 4.2 K to RT showed their magnetic ordering took place at much higher temperature than that of bulk zinc ferrite. Mössbauer measurements that cover the temperature range 4.2 K to room temperature were acquired in zero field and an applied magnetic field of 5 T. The large increase of TN for nanoparticles can be attributed mainly to the redistribution of Fe and Zn cations on the A and B sites. Nanoparticles with smaller size have bigger θYK (Yaffet–Kittel angle). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Developers of the hepatitis B vaccine.
air at VA facilities, one of the many pieces of unfinished business beyond those major issues that we discussed in our Commentary. We agree that all facilities where current and past military personnel serve and receive treatment should be 100% smoke-free and note the recent Institute of Medicine report Combating Tobacco in Military and Veteran Populations. The report, which was commissioned by the Department of Defense (DOD) in 2007, calls for the DOD to set a timeline to eliminate smoking on military installations. The report also recommends that the DOD stop selling tobacco products in military commissaries and exchanges, prohibit tobacco use anywhere on military installations, and treat tobacco use in the same way as other health-related behaviors, such as alcohol abuse and poor physical fitness. We join Matthews and the Institute of Medicine in urging the VA and the DOD to take more immediate steps to protect the health of the men and women who serve in the armed services, as well as the civilians (such as Dr Matthews) working to serve them.