Magnetic properties and phase evolution of PrFeB nanocomposites by refractory element substitution

Abstract

PACS 75.30. Kz, 75.50.Kj, 75.50.Ww, 75.60.Gh Magnetic properties, phase evolution, and coercivity mechanism of Pr deficient and B excess Pr 9.5 Fe 80.5 B 10 ribbons by refractory elements substitution have been investigated. From thermal magnetic analysis (TMA), it was found that all the selected refractory elements (Cr, Nb, V, Ti and Zr) were easy to react with excess boron and retard the formation of [3,4], with excellent remanence B r and maximum energy product (BH) max have been investigated extensively for making bonded magnets. Boron concentration with either low (~ 5-7 at%) [5][6][7][8][9] or extreme high (~16 -20 at%) [10,11] in Pr-lean PrFeB series ribbons are normally selected to develop α-Fe/Pr 2 Fe 14 B and Fe 3 B/Pr 2 Fe 14 B types nanocomposites, respectively, by melt spinning, in various research groups [5][6][7][8][9][10][11], but the intrinsic coercivity i H c of those nanocomposites obtained so far is quite lower, resulting from the existence of considerable amount of magnetically soft phases α-Fe or Fe 3 B. These magnets for higher temperature (T > 100 o C) applications are constrained by lack of sufficient i H c , hence, coercivity needs to be further increased for some practical usages.Higher i H c of 9.5 to 14.3 kOe, B r and (BH) max values of 8.4 to 9.6 kG, and 13.4 to 16.2 MGOe, respectively, have been obtained on the B-enriched ternary Pr 9.5-11.76 Fe bal. B 10 ribbons in our previous studies [12,13]. Among them, Pr 9.5 Fe 80.5 B 10 melt spun ribbon exhibits excellent magnetic properties of B r = 9.6 kG, i H c = 8.3 kOe and (BH) max = 16.2 MGOe. However, large volume of metastable Pr 2 Fe 23 B 3 and Fe 3 B phases are still existed in the ribbons, which suggests the coercivity, i H c , of Pr 9.5 Fe 80.5 B 10 nanocomposites can be enhanced further by reducing the volume fraction of those two magnetically soft phases.In

Dimer-monomer model on the Sierpinski gasket

“…Compare the present results with those in Ref. [36], we find that the number of dimermonomers on the Sierpinski gasket SG d (n) is less than that of spanning trees in general. We give the recursion relations for the generalized two-dimensional Sierpinski gasket SG 2,3 (n) here.…”