Magnetic property and microstructure of SmCo magnetic recording films

Cr/SmCo/Cr thin films with Sm concentration of 37.7 at.% were deposited on glass substrates by magnetron sputtering. Measurement of magnetic properties showed that the SmCo film possessed good magnetic anisotropy, a high coercivity of 3019 kA/m and low magnetic exchange coupling. Microstructure analysis showed that crystallized SmCo5 magnetic phase, non-magnetic SmCo2 phase and Sm2Co7 phase co-existed in the film. The non-magnetic SmCo2 phase might function as isolator of SmCo grains, leading to a decrease of magnetic exchange coupling. Moreover, a Cr2O3 oxide layer which could protect the SmCo layer from oxidation formed at the surface of the Cr cap layer.

Nanocrystalline exchange-coupled Pr-Fe-B permanent magnets

Nanocomposite Pr2Fe14B/α-Fe permanent magnets were prepared by melt spinning and subsequent crystallizahon of Pr8Fe86B6, amorphous Precursnors. The microstructure is a two-phase nanocomposite of Pr2 Fe14 B and softmagnetic α-Fe with an average size of 30nm. X-ray diffration, Thermomagnetic analysis and TEM analy0sis indicatetha amorphous Pr8Fe86B6, alloy crystallizes through the process of Am→Am→Am'+α-Fe→Pr2Fe23B3+α-Fe-Pr2Fe14B+α-FeThe highest value of remanence (Br), cocreivity (Hci) and maximum energy Product ((BH)max) of the nanocrystallinealloys are 1.10T, 340 kA/m and 110 kJ/m3 respechvely, exhibihng remarkable remanence enhancement. The effect ofannaling temperature and time on the microstructure and magnetic properties was also studied. The resultS show thatappropriate annealing temperature and time are important for obtaining the optimal microstructure and the bestmagnetic properties.

Evolution of structure and magnetic properties in PrCo_5 magnet for high energy ball milling in ethanol

High energy ball milling(HEBM) is employed to produce nano-sized grains and particles. In this paper, the structure and magnetic properties are investigated in PrCo5 alloy for HEBM in an ethanol milling medium. With the increase of milling time, the grain size reduces and the coercivity increases. For a milling time of less than 30 min, the hysteresis loop of the aligned sample is very different from that of the un-aligned sample and it does not show a large decrease in magnetization slope, indicating a relatively good alignment of easy axes in particles due to the fact that the texture is nearly well preserved. However, when the milling time is further prolonged, the textured structure deteriorates in the powders.Even though exchange coupling exists between grains within the particle, the magnetic properties are exchange-decoupled between particles and the dipolar interaction results in a negative value of δ m in the whole range of the magnetic field.

Anisotropic nanocomposite soft/hard multilayer magnets

Experimental and theoretical researches on nanostructured exchange coupled magnets have been carried out since about 1988. Here, we review the structure and magnetic properties of the anisotropic nanocomposite soft/hard multilayer magnets including some new results and phenomena from an experimental point of view. According to the different component of the oriented hard phase in the nanocomposite soft/hard multilayer magnets, three types of magnets will be discussed：1） anisotropic Nd2Fe（14）B based nanocomposite multilayer magnets, 2） anisotropic SmCo5 based nanocomposite multilayer magnets, and 3） anisotropic rare-earth free based nanocomposite multilayer magnets. For each of them, the formation of the oriented hard phase, exchange coupling, coercivity mechanism, and magnetic properties of the corresponding anisotropic nanocomposite multilayer magnets are briefly reviewed, and then the prospect of realization of bulk magnets on new results of anisotropic nanocomposite multilayer magnets will be carried out.