Curie temperature rare earth elements

Figure 10 presents the Curie temperature (T ) vs the TM-content (x) for Co- and Fe-based biaary alloys. Alloying rare-earth elements with small amounts of transition metals (x < 0.2) leads to a decrease ia Curie temperature. This is particularly obvious ia the Gd—Co system where it corresponds to a nonmagnetic dilution similar to that of Cu (41,42). This iadicates that TM atoms experience no exchange coupling unless they are surrounded by a minimum number j of other TM atoms. The critical number is j = 5 for Fe and j = 7 for Co. The steep iacrease of for Co-based alloys with x about 0.7 is based on this effect. 

The Curie temperature of R2Fei4B compound with a nonmagnetic rare-earth element (0A, = 0, 0A7. , = 0) can be determined from the condition ... 

The magnetic moments of rare earth elements are caused by the unpaired electrons in their 4f shells. These shells" are shielded by the outer shells so that chemical bonding has relatively little effect on the magnetic moments of these elements. The rare earths form a series of Laves phases of composition MB2 (M = rare earth, B = precious metal) which share the characteristic of ferromagnetic coupling at low temperatures (7). Figure 13 shows the Curie temperatures of a series of com-... 

All f 2Cu2ln indides order ferromagnetically with Curie temperatures between 26.7 and 85.5 K. Strong crystal field anisotropies result in Tc values that do not scale with the de Getmes frmction of the rare earth elements (Fisher et al., 1999). Dy2Cu2ln shows a second phase transition to an antiferromagnetic ground state at 7n = 22 K. 

A well-known method to increase the coercivity in Nd-Fe-B magnets is to substitute the heavy rare-earth (HREE) elements like Dysprosium (Dy) and Terbium (Tb) for Nd (Dhakal et al. 2014 Hirosawa et al. 1986 Hirota et al. 2006). Substitution with dysprosium also raises the Curie-point for these magnets, so that they can be used at higher temperatures. The amount of dysprosium in neodymium magnets may vary from 0.8 to 1.2 % (NdFeB-info.com 2015). 

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