Coercivity of Sm(Co0.9Cu0.1)4.8 melt-spun ribbons

52.7 kOe high coercivity in Sm(Co0.9Cu0.1)4.8 melt-spun ribbons

“…The observed variation in residual magnetization (M r ) can be easily correlated to the magnetization behaviour (Figure 1(a)). When the coercivity values between our 6,7 earlier observation and current once are compared, it can be see that similar values of coercivity are obtained in samples with WS of 15, 30 and 40 m/s, whereas, in 5 m/s sample a reduced coercivity was observed which may be due to microstructural inhomogeneities in the samples spun at low wheel speed. On the other hand, a high coercivity of 52.7 kOe in the WS of 50 m/s sample -an enhancement of ∼10 kOe from our earlier measurement 6,7 -has been observed.…”

“…The microstructure of samples with WS of 15 and 30 m/s has already been presented in our earlier paper. 6,7 The TEM micrograph of the high coercive 50 m/s WS sample is presented in Figure 3. The bright field (BF) micrograph (Figure 4(a)) shows equiaxed fine grains as expected, with a grain size ranging from 40 to 100 nm, whereas the average grain (coherent diffracted domain size from XRD) size was found to be 55 nm.…”

“…6,7 In the present work, the magnetic measurements of all samples were carried out using the high field vibrating sample magnetometer (VSM) with a maximum field of 115 kOe (M/s Oxford, UK). In addition to routine magnetic measurements, minor loop and recoil measurements were also carried out.…”

“…In this context melt-spinning technique provides an alternate approach to develop high coercive single phase magnets. [4][5][6][7] It was also reported that the Cu stabilises 1:7 phase. 8,9 For high coercivity in SmCo 5 magnets, the following structure-property correlations have been understood through detailed studies: i) the presence of high anisotropic SmCo 5 single phase as the matrix, 10 ii) availability of a thin layer of nonmagnetic grain boundary phase to reduce inter-grain magnetic exchange coupling between the neighbouring grains, 11,12 iii) fine grain structure with average grain size in the range of a single domain size (750 nm) to suppress the nucleation of domain walls within the grains, 13,14 and iv) evenly distributed domain wall pinning centres (defects, precipitates and low or high anisotropic secondary phases) within the matrix where the pinning center size is in the range of domain wall thickness of SmCo 5 phase (∼3-4 nm).…”

“…8,9 For high coercivity in SmCo 5 magnets, the following structure-property correlations have been understood through detailed studies: i) the presence of high anisotropic SmCo 5 single phase as the matrix, 10 ii) availability of a thin layer of nonmagnetic grain boundary phase to reduce inter-grain magnetic exchange coupling between the neighbouring grains, 11,12 iii) fine grain structure with average grain size in the range of a single domain size (750 nm) to suppress the nucleation of domain walls within the grains, 13,14 and iv) evenly distributed domain wall pinning centres (defects, precipitates and low or high anisotropic secondary phases) within the matrix where the pinning center size is in the range of domain wall thickness of SmCo 5 phase (∼3-4 nm). 15 Suresh et al 6,7 have studied Sm(Co 0.9 Cu 0.1 ) 4.8 melt-spun ribbons using 55 kOe SQUID magnetometer and reported a coercivity of 42.6 kOe in ribbons with wheel speed (WS) of 50 m/s, and the reasons for such high coercivity have been attributed to i) the formation of fine grain size, ii) the absence of unwanted phases, and iii) the presence of more fraction of 1:5 grains. As it is well known that the coercivity in SmCo 5 magnet is strongly dependent on the applied magnetizing field, samples melt spun with various wheel speeds (5,15,30,40 and 50 m/s) in higher fields of 115 kOe.…”