Magnetic properties and microstructure of SmCo5+α-Fe nanocomposite magnets prepared by mechanical alloying

Effect of sintering temperature on the structure and magnetic properties of SmCo5/Fe nanocomposite magnets prepared by spark plasma sintering

“…At higher sintering temperatures, one can notice that the SmCo 5 matrix consists of uniform distribution of bright phase (Sm-rich) along with the increasing proportion of black phase (Fe(Co)). The transformation of SmCo 5 to Sm 2 Co 17 phase can be generally expected during sintering or annealing at sufficiently higher temperaturesas reported in earlier studies [4,18]. Besides, attempts have been also made on the diffusion of a-Fe with the SmCo-phases during the SPS process using the Mö ssbauer spectroscopy.…”

“…For the bulk samples, regardless of the sintering temperature, all the XRD patterns can be indexed to the SmCo 5 and a-Fe phases. There are some shifts in the peaks of SmCo 5 and a-FeCo phases observed in the XRD patterns and this could be probably due to the inter-diffusion of Fe and Co between the SmCo 5 and a-Fe phases, occurred either during milling or sintering of the NC powders [18,20]. With the increase in SPS temperature, the XRD peaks become more intense and sharper -indicating the crystalline nature of the bulk samples.…”

“…The a-Fe powder of about 10 wt% was selected for mixing with SmCo 5 powder for ball milling; as this fraction of a-Fe has been reported to yield relatively high coercivity and magnetization in isotropic NC magnets [4,18]. Milling was performed in a planetary ball mill (Fritsch pulverisette) with the milling vial and balls made of tungsten carbide.…”

Structural and Mössbauer studies on mechanical milled SmCo5/α-Fe nanocomposite magnetic powders

“…It should be recalled that the VSM measurements always impart the magnetization values e which are cumulative of all the magnetic phases present in the powder samples; on the other hand, the Mössbauer experiments can resolve the individual magnetic contribution of Fe atoms and their local interaction with their nearest neighbours. Although it is quite difficult to estimate the actual composition of Fe(Co) phase, we believe that the possibility of obtaining a-Fe(Co) phase with more (>30 at%) Co content could be favored with longer milling duration based on the previous studies [5,6]. The Mössbauer results obtained in the present study can be considered as a direct evidence to confirm the formation of the a-Fe(Co) phase during milling and interestingly the soft magnetic phase will have a large saturation magnetization which can further enhance the ultimate magnetic properties of the exchange coupled nanocomposite magnets.…”

“…Recently, it has been demonstrated that enhanced magnetization can be obtained in mechanically milled and spark plasma sintered SmCo 5 þ 10e15 wt% Fe nanocomposite magnet [4e6]. Despite the fact that Fe has very limited solubility in SmCo 5 phase [7], nearly a single-phase magnetic behavior is seen for the SmCo 5 /a-Fe nanocomposite magnetsdimplying a strong magnetic coupling between the soft and hard phases [6,8]. It is presumed that during mechanical milling of SmCo 5 and Fe powders, some amount of Fe could be probably dissolved in the SmCo 5 crystal lattice.…”