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Structure and Magnetic Properties of Pr(Fe,Co,Ti,Cu,Zr) 9.66
Melt-spun Nanostructured Alloys
M. Gjoka 1 *, D. Niarchos 1 , C. Sarafidis 2 , O. Kalogirou 2 , M. Grigoras 3 , N. Lupu 3 and H. Chiriac 3
1 Institute of Materials Science, N.C.S.R. “Demokritos” Agia Paraskevi 15310 Athens, Greece
2 Dept. of Physics, Aristotle University of Thessaloniki, 54 124 Thessaloniki, Greece
3 National Institute of R&D for Technical Physics, 47 Mangeron Blvd., 700050 Iasi, Romania
* gjoka@ims.demokritos.gr
Abstract
Pr(Fe,Co,Ti,Cu,Zr) 9.66 alloys were prepared by the melt-spinning technique with a velocity of 40 and 30 ms −1 . Annealing of
the melt-spun ribbons resulted in the formation of hexagonal TbCu 7 -type structure. The saturation magnetization of the
TbCu 7 -type phase was found to be 152.0 Am 2 kg −1 at room temperature. The annealed ribbons have low coercivity values
attributed to the presence of the soft α-Fe(Co) phase (under certain experimental conditions).
1. Introduction
Nanophase materials have attracted considerable interest in the last few years [1] because of their unusual scientific and
technological properties. The breakthrough for the search on nanophase materials using the melt-spinning technique, by
Hadjipanayis et al. and Croat et al., remain important up today for the production of nanophase magnets. One of the rare
earth compounds for the new permanent magnet applications is the R 3 (Fe,M) 29 (R: rare earth and M: transition metal) phase.
This R 3 (Fe,M) 29 phase is described as an alternate stacking of the R(Fe,M) 12 phase (tetragonal ThMn 12 -type structure) and the
R 2 (Fe,M) 17 phase (rhombohedral Th 2 Zn 17 -type structure. There are some reports of melt-spinning on the Re 3 (FeT) 29 system
(R = Ce, Pr, Nd and T = Ti, Cr) [2- 5 ]. Sm(Co bal Fe 0.19 Cu 0.1 Ti 0.05 ) 9.66 melt-spun powder magnets have been fabricated [6]. In
this work we report the production and magnetic properties of the Pr[Fe x Co 0.284 Ti z Cu w1 Zr w2 ] 9.66 (x+z+w 1 +w 2 = 0.716) meltspun
nanostructured alloys.
2. Experimental
Pr[Fe x Co 0.284 Ti z Cu w1 Zr w2 ] 9.66 (x+z+w 1 +w 2 = 0.716) alloys were prepared by arc melting in an argon atmosphere. Small
quantities of the alloy ingots were placed in a quartz crucible with an orifice of 0.6 mm in diameter at the bottom. The alloy
ingots were induction-melted in an argon atmosphere and then ejected through the orifice under argon pressure onto a
chromium-plated copper wheel rotating at a surface velocity of 40 and 30 ms −1 . The resultant melt-spun ribbons were
obtained as fragmented pieces. Typical dimensions of the ribbon fragments were 10 µm in thickness by 1 mm wide and 10-
20 mm long. Heat treatments of the melt-spun ribbons were then carried out in an argon atmosphere at temperatures between
700-850 0 C K for different times. The specimens were examined by X-ray powder diffraction (XRD) using CuKα radiation.
The magnetization of the powders was examined at a heating rate of 5°C/min in vacuum using a vibrating sample
magnetometer (VSM) at an applied field of 200 Oe. The hysteresis loops of the specimens were measured at room
temperature by VSM under a maximum applied field of 2.0 Tesla.
3. Results and discussion
Intensity (arb. units)
a)
b)
c)
(101)
(110)
(111)
(002)
20 40
2-theta (degree)
(200)
(201)
Fig. 1 XRD of Pr(Fe,Co,Ti) 9.66 a)
theoretical pattern of TbCu 7 phase, b)
as-spun (v=40 ms- 1 ) and c) powdered,
Tc 1
Alloys with the composition R 3 (Fe,Co,Ti) 29 or R(Fe,Co,Ti) 9.66 can exist in
two crystal structures depending on the preparation technique [2]. The XRD
patterns of the asspun
ribbons
(v=40 ms -1 ), Fig. 1
(b, c)), were
a) ann. 800 0 C
similar to those
Tc 3
reported in [2] for
melt-spun samples
with the 3:29
nominal stoichiometry.
In the
b) as-cast
Tc Tc
2
4
latter, the authors
describe this
pattern as corresponding
0 300 600
Temperature ( 0 C)
900
to the
hexagonal TbCu 7
Fig. 2 MvsT of as-cast and annealed ribbons (v=40
ms- 1 )
structure.
Qualitative
analysis of XRD
patterns, Fig 1(b,
c) indicate that the samples are partially crystallized. The main phase on the
as cast ribbons is that of hexagonal TbCu 7 -type structure for our range of
Magnetisation (arbitray units)
92