Improvement of energy product in exchange coupled Fe49−xCoxPt51 (x=0.0,0.7,1.3,2.2) thin films

Abstract

Magnetic properties and crystal structure of the Fe49−xCoxPt51 (x=0.0,0.7,1.3,2.2) thin films deposited on a quartz substrate heated at 500°C were investigated. A significantly enhanced energy product of 18.4MGOe (87% larger than that of the binary film) was obtained in the x=1.3 sample. This improvement can be attributed to the well exchange coupling between the Ll0 and the residual disordered FePt regions. Unlike the common exchange spring (coupled) magnets or films showing a well defined two-phase structure, the chemical ordering of Fe–Co–Pt films changes continuously from the ordered regions to the disordered regions. We consider that this continuous change of chemical ordering enhances exchange coupling. Furthermore, the addition of cobalt also accompanied the decrease of crystal domain (subgrain) size in FePt grains. The fine-grain dispersion also can be a reason for the high energy product.

Micromagnetic simulation of Sm—Co/α-Fe/Sm—Co trilayers with various angles between easy axes and the film plane

“…Experimental energy products, however, turn out to be much lower than the theoretical one, even smaller than the sintered Nd-Fe-B. An energy product paradox is proposed therefore in some literature, which has been intensively studied in both experimental [18][19][20][21][22][23][24] and theoretical [25][26][27][28][29][30][31] works by scientists. Further, the price of rare-earth materials rose rapidly in the last few years, which gives the investigation of the composite nanomagnets another push.…”

Thickness effect on structural and magnetic properties in Fe49−xPt51Cox (x=0.0, 1.3) thin films

“…The lower ordering introduces more residual disorder phase which increases magnetization. The refined magnetic particles enhance the intergranular exchange coupling between order and disorder region [5]. Summarized with the structural and magnetic results, the explanations for the high energy product obtained in the Co-added films are suggested to be the moderate ordering and refined grain structure.…”

“…Experimentally, Liu et al [3] succeeded in fabricating a FePt-Fe 3 Pt nanocomposited thin films with a very high (BH) max of 52.8 MGOe by rapidly annealing Fe/Pt multilayer thin films. Recently, Takahashi et al [4] reported the exchange coupling effect in the polycrystalline FePt/Fe bilayer thin films can significantly enhance energy product.In our previous work [5], energy product has been successfully enhanced in equi-composite Fe-Pt thin film by doping of Co. The optimum concentration of dopant is 1.3 at%.…”

“…In our previous work [5], energy product has been successfully enhanced in equi-composite Fe-Pt thin film by doping of Co. The optimum concentration of dopant is 1.3 at%.…”

Effect of exchange coupling on magnetic property in Sm–Co/ α -Fe layered system

“…Since an exchange-coupled composite material was proposed by Kneller in 1991, [1] with a hard phase to provide high coercivity and a soft phase to provide high saturation and remanence, the coercivity, structural, and magnetic properties in permanent magnets have always been an important topic in magnetism. [2][3][4] An energy product paradox was proposed in some literatures, which has been intensively studied in both experimental [5][6][7][8] and theoretical [9][10][11][12][13][14][15] works by condensed matter physicists. A lot of works have been devoted to the exploration of the largest energy product experimentally reachable.…”