Formation of strong L1₀-FePd/α-Fe nanocomposite magnets by visualizing efficient exchange coupling

Abstract

FORC analysis distinguished a microscopically undetectable difference in phase-segregation structure in nanocomposite magnets, finding both efficient and inefficient exchange coupling.

Synthesis of mesoscopic particles of multi-component rare earth permanent magnet compounds

“…One is to adopt materials with a large 1 but a consequently small w , such as L1 0 -FePt [152], Nd 2 Fe 14 B [153,154], SmCo 5 [87,[155][156][157][158], and Sm 2 Fe 17 N 3 [150], as their large a compensated for a small s corresponding to a small s ( s < ca.10 nm) [148,149]. Another is to adopt materials with a moderate 1 and a consequently relatively large w , such as L1 0 -FePd [159][160][161] and HfCo 7 [148,149,161,162]. The latter approach is not usually considered, since the gain in α is overcompensated by the reduction of a .…”

“…Apart from the microstructure issues above, the most obvious obstacle to the synthesis of R-T/T NCMs is the formation of undesirable phases as the R and T metals can form many equilibrium and metastable phases. The design of magnetically hard/soft exchange-coupled NCMs with the soft phase as an equilibrium phase of the hard phase, which is similar to the one that was proved to be so effective in L1 0 -FePd/Fe NCMs [159][160][161], is a solution. MMPs can be magnetically aligned to form the anisotropic NCMs.…”

“…Another is to adopt materials with a moderate and a consequently relatively large , such as L 1 0 -FePd [ 159–161 ] and HfCo 7 [ 162 ], as they had benefitted to and , and a large corresponding to a large ( < ca. 20 nm) could be compensated for a moderate [ 148 , 149 , 161 , 162 ]. The latter approach is not usually considered, since the gain in is overcompensated by the reduction of .…”

“…It has been demonstrated that the anisotropic FePt/Fe 0.8 Ni 0.2 NCMs could enhance by 224% of that of the corresponding isotropic NCMs [ 163 ]. Therefore, chemical synthesis of particulate NCMs, which is similar to the ones that were proved to be so effective in L 1 0 -FePd/Fe NCMs [ 161 ] and HfCo 7 /Fe 65 Co 35 NCMs [ 162 ], is of crucial importance to fabricate the anisotropic NCMs with ultra-large . In a typical synthesis [ 157 ], particulate SmCo 5 /Co MMPs (200 nm, Co-soft phase: 4 wt.%) were synthesized by Ca R–D of Sm[Co(CN) 6 ]⋅4H 2 O@GO MMPs and Co(acac) 2 additive at 960°C; their isotropic sample showed room-temperature of 2.07 T, of 0.75, and of 80 (10 MG Oe).…”

“…It has been demonstrated that the anisotropic FePt/Fe 0.8 Ni 0.2 NCMs could enhance ( ) maxby 224 % of that of the corresponding isotropic NCMs[163]. Therefore, chemical synthesis of particulate NCMs, which is similar to the ones that were proved to be so effective in L1 0 -FePd/Fe NCMs[161] and HfCo 7 /Fe 65 Co 35 NCMs[162], is of crucial importance to fabricate the anisotropic NCMs with ultra-large ( ) max .…”