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Synthesis and magnetic properties of R3(Fe,Ti)29 and R3(Fe,Ti)29Nx (R = Ce,Pr,Gd)
ELSEVlER
Journal of Magnetism and Magnetic Materials 147 (1995) L7-LlO
Letter to the Editor
Synthesis and magnetic properties of R,( Fe,Ti) 29 and R,( Fe,Ti) 29N, ( R = Ce,Pr,Gd) 0. Kalogirou
*,
V. Psycharis, M. Gjoka, D. Niarchos
Institute of Materials Science, National Centre for Scientific Research ‘Demokritos’, 153 10 Ag. Paraskeui, Attiki, Greece Received 3 November 1994; in revised form 20 February 1995
Abstract R,(Fe,Ti), and R,(Fe,Ti),,N, nitrides (R = Ce,Pr,Gd) have been synthesized. The structure is described in the A,,, space group. The unit cell dimensions change as a function of rare-earth reflecting the lanthanide contraction, except for Ce, which has anomalously low lattice parameters. The unit cell volumes of the nitrides are 5-7% greater than those of the parent alloys. The Curie temperature increases from Ce to Gd with values of 330, 392 and 524 K for Ce, Pr and Gd respectively, and is enhanced by nitrogenation to 670 K for Ce, 721 K for Pr, and 745 K for Gd. The room temperature magnetization at 5 T is 92.0, 130.75 and 86.58 Am*/kg and increases to 151.88, 164.47 and 118.0 Am2/kg after nitrogenation for Ce, Pr and Gd respectively.
1. Introduction Recently, much attention has been paid to the novel rare-earth iron intermetallic compound R,(Fe,T),, (R = Ce, Pr, Nd, Sm and T = Ti, V, Cr, Mn and MO) and their nitrides [l-8]. Among them, the Sm,(Fe,Ti),,N, nitride seems to be a potential candidate for use in permanent magnets [lo]. In a previous article [12] we have shown that the Nd,(Fe,Ti),,-type structure can be described more accurately in the A z,m space group than in the P2,,, proposed in Ref. [5], and that the nature of the magnetocrystalline anisotropy of Nd,(Fe,Ti),, and Nd,(Fe,Ti),,N, is that of an easy-cone-type. We have also shown that the number of atoms in the 3 : 29 nitrided phase is four nitrogen atoms per chemical formula. In the present work, we synthesized the
* Corresponding author.
R,(Fe,Ti),, alloys and R,(Fe,Ti),,N, nitrides for R = Ce, Pr and Gd, and studied their magnetic properties. We also prepared the Sm-alloy and nitride in order to compare it with the other series members.
2. Experimental Ingots were prepared by arc-melting elemental constituents of high purity (99.9%), with the starting composition R,Fe,,,,Ti,,, and R,Fe,,Ti, (R = Ce, Pr, Sm and Gd), subsequently followed by annealing (wrapped in tantalum foil) in vacuum at 1273-1423 K for three days and then fast quenching in water. The best samples were obtained at 1323 K for Ce and Pr, 1373 K for Sm, and 1348 K for Gd, and for Ti = 1.5. The ingots were ground into fine powder ( < 37 pm). The gas-phase reaction between the alloy powders and high purity nitrogen gas was
0304-8853/9.5/$09.50 0 1995 Elsevier Science B.V. All rights reserved .SSDI 0 3 0 4 - 8 8 5 3 ( 9 4 ) 0 1 6 4 7 - X
0. Kalogirou et al. /Journal
of Magnetism and Magnetic Materials 147 (1995) L7-LlO 12.00 - a3 tPe,Ti)zg N,
G&(Fe,Ti),,
??
R3 (Fe.Ti)Zg
44
34
2%e+o
Ce
Pr
Nd
Sm
Gd
Fig. 1. XRD spectra of Ra(Fe,Ti),,.
Fig. 2. Unit cell parameters for R,(Fe,Ti),, and Rs(Fe,Ti)a,N,.
carried out at 673 K for 12 h. The phase composition of the samples was identified by X-ray powder diffraction (XRD) using CuKp radiation and the Curie temperature was determined by thermomagnetic analysis (TMA). Magnetization values were derived from the magnetization curves in fields up to 5 T by a Quantum Design SQUID magnetometer.
1 : 12 phase was calculated to be 21.5 and 14.7% for Ce and Gd respectively, and that of a-Fe 1.5% in both cases. Nitrogenation resulted in a cell volume enhancement of 5--7% for all alloys. As we have shown in Ref. [ 121, these values indicate that nitrogen insertion reached its maximum value, i.e., four nitrogen atoms per unit formula. In the XRD patterns of the nitrided samples only the shifted peaks were observed and not any of the parent compound. In the TMA measurements only the Curie temperatures of the nitrided phases were detected indicating that there was no amount of unreacted parent compound. Thus, it was concluded that the samples were fully nitrided. In Table 1 the lattice parameters, the unit cell volume and the relative change in unit cell volume AV/V upon nitrogenation are given. In Figs. 2 and 3 the dependence of the unit cell dimensions, of the parent
3. Sample preparation and characterization X-ray diffraction patterns of the annealed alloys show that the R,(Fe,Ti),,-type structure dominates (Fig. 1). The P r- a11 oy is single phase except for a little a-Fe inside, 4.6% as calculated from Rietveld analysis. In the Ce- and Gd-alloys a secondary phase of the ThMn,,-type structure and a little a-Fe was detected. From the Rietveld analysis the extent of the
Table 1 Lattice parameters a, b, c and p, the unit cell volume V and the relative change in the unit cell parameters upon nitrogenation As/a, Ah/b, AC/C and AV/V of R,(Fe,Ti),, and R,(Fe,Ti),,N, V(K)
As/a(%)
Compound
a (A)
Ce,(Fe,Ti),, Ce&Fe,Ti)a,N, Pr,(Fe,Ti),, Pr,(Fe,Ti),,N, Nd,(Fe,Ti),, Nd,(Fe,Ti),,N, Sm3(Fe,T$, Sm&Fe,Ti),,N, Gd,(Fe,Ti),, Gd3(Fe,Ti)a,N,
9.696(l) 96.82(l) 866.82 10.571(l) 8.517(l) 97.39(2) 927.19 2.44 10.829(4) 8.725(4) 9.893(3) 96.92(l) 8.601(l) 9.755(l) 886.85 10.647(l) 97.80(l) 937.43 2.35 10.897(2) 8.774(4) 9.896(5) 10.6382(5) 8.5892(4) 9.7456(5) 96.930(2) 8 8 3 . 9 8 97.29(l) 930.37 1.99 8.735(3) 9.896(4) 10.850(4) 9.721(2) 96.96 878.1 10.625(2) 8.564(l) 926.49 2.04 10.842(4) 8.73(3) 9.868(4) 97.31(3) 873.74 ~ 10.6073(8) 8.5458(6) 9.7107(8) 96.97(l) 97.13 927.06 2.11 10.833(4) 8.725(5) 9.884(7)
b 6,
c (3
p (“I
Ah/b(%)
AC/C(%)
_ 2.44 _ 2.01 _ 1.70 _ 1.94 _ 2.11
_ 2.03 _ 1.45 _ 1.45 _ 1.51 _ 1.81
AV/V(%) 6.96 _ 5.7 _ 5.25 _ 5.52 _ 6.1
L9
0. Kalogirou et al. /Journal of Magnetism and Magnetic Materials 147 (1995) L7-LlO 1000.00
and the nitrided compounds, on the rare-earth is shown. The values for Nd were taken from Ref. [12]. It is characteristic that there is a change in the cell dimensions as a function of rare-earth reflecting the lanthanide contraction, except for the anomalously low lattice parameters of Ce, and that the lattice expansion is anisotropic depending on the kind of rare-earth. Such a behaviour has been observed in the case of the 1: 12 and 2: 17 phases [19-211. Among the other R,(Fe,Ti),, compounds the Ce nitride shows the largest volume expansion indicating a mixed 4f configuration.
o R3 (Fe,Ti)Zg N, . R3 (FeJOpg
960.00 ,‘J
r
3
2 920.00 $ ??
880.00
?
?
?
?
840.00 i
I Ce
I Pr
I
Nd
I
I
I Stll
I Gd
Fig. 3. Unit cell volumes for R,(Fe,Ti&, and R,(Fe,Ti),,N, 200
1
800,
(al 5K
M =z
600
+++’ ,+++ +* .
160
+*
+ **+i+ +i+* . . 8”
a
3
aL
. ...*
..
. ...*
Ce alloy
. Pr
Nd
Sm
+ .
Ce nitride Pr nitride
A Gd nitride
4
6
H CT)
Gd
Fig. 4. Curie temperature of R,(Fe,Ti)a, and Rs(Fe,Ti),,N, compared to those of RFe,,Ti and RFe,,TiN,, and R,Fe,, and
Gd alloy
2
0
Ce
Pr alloy
. . . . ..*..
___ fbl
RaFet,N,. 300K
Table 2 Curie temperature and magnetization values at 5 and 300 K in a field of 5 T for R,(Fe,Ti),, and R,(Fe,Ti),,N, (in brackets)
RE
(Am* /kg)
ATc/Tc
La,.
Tc
MST
(K)
(K)
5K
300 K
(%o)
Ce
1323 1323
Nd
1373
Sm
1373
134.0 (165.31) 151.8 (171.16) 159.4 (180.03) 134.28 (160) 98.65 (121.0)
92.0 (151.88) 130.75 (164.47) 135.78 (163.58) 121.64 (140) 86.58 (118.0)
100
Pr
330 (670) 392 (721) 437 (712) 488 (750) 524 (745)
Gd
1348
84 63
. Gd alloy
54
00 0
2
* Gd nitride
4
6
H (‘U
42
Fig. 5. Magnetization curves of powder samples of R,(Fe,Ti),, and R,(Fe,Ti),,N, at 5 K (a) and at 300 K (b).
LlO
0. Kalogirou et al. /Journal of Magnetism and Magnetic Materials 147 (199.5) L7-LIO
4. Magnetic properties Curie temperature (Tc) values for R,(Fe,Ti),, and R,(Fe,Ti),,N, were determined by thermomagnetic analysis (TMA) with a heating rate of S”C/min and are listed in Table 2. The presence of the secondary 1: 12-phase in the Ce- and Gd-alloys was observed in the TMA curve. Fig. 4 shows that the Curie temperature depends on the kind of the rare-earth for both the parent and the nitrided compounds. This behaviour is characteristic for both R,Fe,, [19] and R(Fe,Ti),, [20,21] compounds and their nitrides. The values for Nd,(Fe,Ti),, were taken from Ref. [12]. The Curie temperature values of R,(Fe,Ti),, and R,(Fe,Ti),,N, are lower than those of RFe,,Ti and RFe,,TiN, and higher than those of R,Fe,, and R2Fe17Nx, respectively. Fig. 5 shows the magnetization curves at 5 and 300 K of R,(Fe,Ti),, and R,(Fe,Ti),,N,. The magnetization values at 5 T are listed in Table 2. The magnetization values for Sm were taken from Ref. [lo].
References [II S.J. Collocot, R.K. Day, J.B. Dunlop and R.L. Davis, Proc.
Dl 131
141
is1
b1 171
181 [91 [lOI
5. Conclusions [Ill
We have reported the synthesis and some of the properties of a novel RE-Fe-T series, R,(Fe,Ti),, with R = Ce, Pr and Gd, and their nitrides. As in other RE-Fe-T intermetallic compounds, such as 1: 12- and 2 : 17-type alloys, nitrogenation enhances the magnetization and Curie temperature. The structural and magnetic properties of R,(Fe,Ti),, and R,(Fe,Ti),,N, depend on the kind of the rare-earth. The synthesis of single phase Ce,(Fe,Ti),, and Gd,(Fe,Ti),, samples, and the complete study of the crystallographic and magnetic properties of the series is in progress and will be published soon.
Acknowledgements This work was partially supported by the B/ECT91-405 project of the EU.
WI [I31 [I41 iI51 iI61 D71
[I81 [191 DO1 ml
7th Int. Symp. on Magnetic Anisotropy and Coercivity in Rare-Earth Transition Metal Alloys, Canberra (1992) pp. 437-444. G.V. Ivanova, Ye.V. Schrebakova, Ye.V. Belozerov, A.S. Yermolenko and Ye.1. Teytel, Phys. Met. Metall. 70 (1990) 63. Ye.V. Schrebakova, G.V. Ivanova, AS. Yermolenko, Ye.V. Belozerov and V.S. Gaviko, J. Alloys Compounds 182 (1992) 199. J.M. Cadogan, H.S. Li, R.L. Davis, A. Margarian, S.J. Collocot, J.B. Dunlop and P.B. Gwan, J. Appl. Phys. 75 (1994) 7114. H.S. Li, J.M. Cadogan, R.L. Davis, A. Margarian and J.B. Dunlop, Solid State Comm. 90 (1994) 487. Z. Hu and W.B. Yelon, Solid State Comm. 91 (1994) 223. F.M. Yang, B. Nasunjilegal, H.Y. Pan, J.L. Wang, R.W. Zhao, B.P. Hu, Y.Z. Wang, H.S. Li and J.M. Cadogan, J. Magn. Magn. Mater. 135 (1994) 298. H.S. Li, Suharyana, J.M. Cadogan and G.J. Bowden, J. Appl. Phys. 75 (1994) 7120. C.D. Fuerst, F.E. Pinkerton and J.F. Herbst, J. Magn. Magn. Mater. 129 (1994) L115. F.M. Yang, B. Nasunjilegal, J.L. Wang, H.Y. Pan, W.D. Qing, R.W. Zhao, B.P. Hu, Y.Z. Wang, G.C. Liu, H.S. Li and J.M. Cadogan, J. Appl. Phys. 76 (1994) 1971. L. Morellon, L. Pareti, P.A. AIgarabeI, F. Albertini and M.R. Ibarra, J. Phys.: Condens. Matter. 6 (1994) L379. 0. Kalogirou, V. Psycharis, L. Saettas and D.N. Niarchos, J. Magn. Magn. Mater. 146 (199.5) 335. J.M. Cadogan, H.S. Li, J.B. Dunlop, D.H. Ryan, S.J. Colollocot and R.L. Davis, J. Appl. Phys. 76 (1994) 6138. CD. Fuerst, F.E. Pinkerton and J.F. Herbst, J. Appl. Phys. 76 (1994) 6144. Z. Hu and W.B. Yelon, J. Appl. Phys. 76 (1994) 6147. L. Pareti, A. Paoluzi, F. Albertini, M.R. Ibarra, L. Morellon and P.A. AIgarabeI, J. Appl. Phys. 76 (1994) 7473. D.H. Ryan, J.M. Cadogan, A. Margarian and J.B. Dunlop, J. Appl. Phys. 76 (1994) 6150. A. Margarian, J.B. Dunlop, R.K. Day and W. Kalceff, J. Appl. Phys. 76 (1994) 6153. Y. Otani, D.P.F. Hurley, Hong Sun and J.M.D. Coey, J. Appl. Phys. 69 (1991) 5584. Y.C. Yang, X.D. Zhang, S.L. Ge, Q. Pan, L.S. Kong, H. Li, J.L. Yang, B.S. Zhang, Y.F. Ding and C.T. Ye, J. Appl. Phys. 70 (1991) 6001. M. Akayama, H. Fujii, K. Yamamoto and K. Tatami, J. Magn. Magn. Mater. 130 (1994) 99.
Journal of Magnetism and Magnetic Materials 147 (1995) L7-LlO
Letter to the Editor
Synthesis and magnetic properties of R,( Fe,Ti) 29 and R,( Fe,Ti) 29N, ( R = Ce,Pr,Gd) 0. Kalogirou
*,
V. Psycharis, M. Gjoka, D. Niarchos
Institute of Materials Science, National Centre for Scientific Research ‘Demokritos’, 153 10 Ag. Paraskeui, Attiki, Greece Received 3 November 1994; in revised form 20 February 1995
Abstract R,(Fe,Ti), and R,(Fe,Ti),,N, nitrides (R = Ce,Pr,Gd) have been synthesized. The structure is described in the A,,, space group. The unit cell dimensions change as a function of rare-earth reflecting the lanthanide contraction, except for Ce, which has anomalously low lattice parameters. The unit cell volumes of the nitrides are 5-7% greater than those of the parent alloys. The Curie temperature increases from Ce to Gd with values of 330, 392 and 524 K for Ce, Pr and Gd respectively, and is enhanced by nitrogenation to 670 K for Ce, 721 K for Pr, and 745 K for Gd. The room temperature magnetization at 5 T is 92.0, 130.75 and 86.58 Am*/kg and increases to 151.88, 164.47 and 118.0 Am2/kg after nitrogenation for Ce, Pr and Gd respectively.
1. Introduction Recently, much attention has been paid to the novel rare-earth iron intermetallic compound R,(Fe,T),, (R = Ce, Pr, Nd, Sm and T = Ti, V, Cr, Mn and MO) and their nitrides [l-8]. Among them, the Sm,(Fe,Ti),,N, nitride seems to be a potential candidate for use in permanent magnets [lo]. In a previous article [12] we have shown that the Nd,(Fe,Ti),,-type structure can be described more accurately in the A z,m space group than in the P2,,, proposed in Ref. [5], and that the nature of the magnetocrystalline anisotropy of Nd,(Fe,Ti),, and Nd,(Fe,Ti),,N, is that of an easy-cone-type. We have also shown that the number of atoms in the 3 : 29 nitrided phase is four nitrogen atoms per chemical formula. In the present work, we synthesized the
* Corresponding author.
R,(Fe,Ti),, alloys and R,(Fe,Ti),,N, nitrides for R = Ce, Pr and Gd, and studied their magnetic properties. We also prepared the Sm-alloy and nitride in order to compare it with the other series members.
2. Experimental Ingots were prepared by arc-melting elemental constituents of high purity (99.9%), with the starting composition R,Fe,,,,Ti,,, and R,Fe,,Ti, (R = Ce, Pr, Sm and Gd), subsequently followed by annealing (wrapped in tantalum foil) in vacuum at 1273-1423 K for three days and then fast quenching in water. The best samples were obtained at 1323 K for Ce and Pr, 1373 K for Sm, and 1348 K for Gd, and for Ti = 1.5. The ingots were ground into fine powder ( < 37 pm). The gas-phase reaction between the alloy powders and high purity nitrogen gas was
0304-8853/9.5/$09.50 0 1995 Elsevier Science B.V. All rights reserved .SSDI 0 3 0 4 - 8 8 5 3 ( 9 4 ) 0 1 6 4 7 - X
0. Kalogirou et al. /Journal
of Magnetism and Magnetic Materials 147 (1995) L7-LlO 12.00 - a3 tPe,Ti)zg N,
G&(Fe,Ti),,
??
R3 (Fe.Ti)Zg
44
34
2%e+o
Ce
Pr
Nd
Sm
Gd
Fig. 1. XRD spectra of Ra(Fe,Ti),,.
Fig. 2. Unit cell parameters for R,(Fe,Ti),, and Rs(Fe,Ti)a,N,.
carried out at 673 K for 12 h. The phase composition of the samples was identified by X-ray powder diffraction (XRD) using CuKp radiation and the Curie temperature was determined by thermomagnetic analysis (TMA). Magnetization values were derived from the magnetization curves in fields up to 5 T by a Quantum Design SQUID magnetometer.
1 : 12 phase was calculated to be 21.5 and 14.7% for Ce and Gd respectively, and that of a-Fe 1.5% in both cases. Nitrogenation resulted in a cell volume enhancement of 5--7% for all alloys. As we have shown in Ref. [ 121, these values indicate that nitrogen insertion reached its maximum value, i.e., four nitrogen atoms per unit formula. In the XRD patterns of the nitrided samples only the shifted peaks were observed and not any of the parent compound. In the TMA measurements only the Curie temperatures of the nitrided phases were detected indicating that there was no amount of unreacted parent compound. Thus, it was concluded that the samples were fully nitrided. In Table 1 the lattice parameters, the unit cell volume and the relative change in unit cell volume AV/V upon nitrogenation are given. In Figs. 2 and 3 the dependence of the unit cell dimensions, of the parent
3. Sample preparation and characterization X-ray diffraction patterns of the annealed alloys show that the R,(Fe,Ti),,-type structure dominates (Fig. 1). The P r- a11 oy is single phase except for a little a-Fe inside, 4.6% as calculated from Rietveld analysis. In the Ce- and Gd-alloys a secondary phase of the ThMn,,-type structure and a little a-Fe was detected. From the Rietveld analysis the extent of the
Table 1 Lattice parameters a, b, c and p, the unit cell volume V and the relative change in the unit cell parameters upon nitrogenation As/a, Ah/b, AC/C and AV/V of R,(Fe,Ti),, and R,(Fe,Ti),,N, V(K)
As/a(%)
Compound
a (A)
Ce,(Fe,Ti),, Ce&Fe,Ti)a,N, Pr,(Fe,Ti),, Pr,(Fe,Ti),,N, Nd,(Fe,Ti),, Nd,(Fe,Ti),,N, Sm3(Fe,T$, Sm&Fe,Ti),,N, Gd,(Fe,Ti),, Gd3(Fe,Ti)a,N,
9.696(l) 96.82(l) 866.82 10.571(l) 8.517(l) 97.39(2) 927.19 2.44 10.829(4) 8.725(4) 9.893(3) 96.92(l) 8.601(l) 9.755(l) 886.85 10.647(l) 97.80(l) 937.43 2.35 10.897(2) 8.774(4) 9.896(5) 10.6382(5) 8.5892(4) 9.7456(5) 96.930(2) 8 8 3 . 9 8 97.29(l) 930.37 1.99 8.735(3) 9.896(4) 10.850(4) 9.721(2) 96.96 878.1 10.625(2) 8.564(l) 926.49 2.04 10.842(4) 8.73(3) 9.868(4) 97.31(3) 873.74 ~ 10.6073(8) 8.5458(6) 9.7107(8) 96.97(l) 97.13 927.06 2.11 10.833(4) 8.725(5) 9.884(7)
b 6,
c (3
p (“I
Ah/b(%)
AC/C(%)
_ 2.44 _ 2.01 _ 1.70 _ 1.94 _ 2.11
_ 2.03 _ 1.45 _ 1.45 _ 1.51 _ 1.81
AV/V(%) 6.96 _ 5.7 _ 5.25 _ 5.52 _ 6.1
L9
0. Kalogirou et al. /Journal of Magnetism and Magnetic Materials 147 (1995) L7-LlO 1000.00
and the nitrided compounds, on the rare-earth is shown. The values for Nd were taken from Ref. [12]. It is characteristic that there is a change in the cell dimensions as a function of rare-earth reflecting the lanthanide contraction, except for the anomalously low lattice parameters of Ce, and that the lattice expansion is anisotropic depending on the kind of rare-earth. Such a behaviour has been observed in the case of the 1: 12 and 2: 17 phases [19-211. Among the other R,(Fe,Ti),, compounds the Ce nitride shows the largest volume expansion indicating a mixed 4f configuration.
o R3 (Fe,Ti)Zg N, . R3 (FeJOpg
960.00 ,‘J
r
3
2 920.00 $ ??
880.00
?
?
?
?
840.00 i
I Ce
I Pr
I
Nd
I
I
I Stll
I Gd
Fig. 3. Unit cell volumes for R,(Fe,Ti&, and R,(Fe,Ti),,N, 200
1
800,
(al 5K
M =z
600
+++’ ,+++ +* .
160
+*
+ **+i+ +i+* . . 8”
a
3
aL
. ...*
..
. ...*
Ce alloy
. Pr
Nd
Sm
+ .
Ce nitride Pr nitride
A Gd nitride
4
6
H CT)
Gd
Fig. 4. Curie temperature of R,(Fe,Ti)a, and Rs(Fe,Ti),,N, compared to those of RFe,,Ti and RFe,,TiN,, and R,Fe,, and
Gd alloy
2
0
Ce
Pr alloy
. . . . ..*..
___ fbl
RaFet,N,. 300K
Table 2 Curie temperature and magnetization values at 5 and 300 K in a field of 5 T for R,(Fe,Ti),, and R,(Fe,Ti),,N, (in brackets)
RE
(Am* /kg)
ATc/Tc
La,.
Tc
MST
(K)
(K)
5K
300 K
(%o)
Ce
1323 1323
Nd
1373
Sm
1373
134.0 (165.31) 151.8 (171.16) 159.4 (180.03) 134.28 (160) 98.65 (121.0)
92.0 (151.88) 130.75 (164.47) 135.78 (163.58) 121.64 (140) 86.58 (118.0)
100
Pr
330 (670) 392 (721) 437 (712) 488 (750) 524 (745)
Gd
1348
84 63
. Gd alloy
54
00 0
2
* Gd nitride
4
6
H (‘U
42
Fig. 5. Magnetization curves of powder samples of R,(Fe,Ti),, and R,(Fe,Ti),,N, at 5 K (a) and at 300 K (b).
LlO
0. Kalogirou et al. /Journal of Magnetism and Magnetic Materials 147 (199.5) L7-LIO
4. Magnetic properties Curie temperature (Tc) values for R,(Fe,Ti),, and R,(Fe,Ti),,N, were determined by thermomagnetic analysis (TMA) with a heating rate of S”C/min and are listed in Table 2. The presence of the secondary 1: 12-phase in the Ce- and Gd-alloys was observed in the TMA curve. Fig. 4 shows that the Curie temperature depends on the kind of the rare-earth for both the parent and the nitrided compounds. This behaviour is characteristic for both R,Fe,, [19] and R(Fe,Ti),, [20,21] compounds and their nitrides. The values for Nd,(Fe,Ti),, were taken from Ref. [12]. The Curie temperature values of R,(Fe,Ti),, and R,(Fe,Ti),,N, are lower than those of RFe,,Ti and RFe,,TiN, and higher than those of R,Fe,, and R2Fe17Nx, respectively. Fig. 5 shows the magnetization curves at 5 and 300 K of R,(Fe,Ti),, and R,(Fe,Ti),,N,. The magnetization values at 5 T are listed in Table 2. The magnetization values for Sm were taken from Ref. [lo].
References [II S.J. Collocot, R.K. Day, J.B. Dunlop and R.L. Davis, Proc.
Dl 131
141
is1
b1 171
181 [91 [lOI
5. Conclusions [Ill
We have reported the synthesis and some of the properties of a novel RE-Fe-T series, R,(Fe,Ti),, with R = Ce, Pr and Gd, and their nitrides. As in other RE-Fe-T intermetallic compounds, such as 1: 12- and 2 : 17-type alloys, nitrogenation enhances the magnetization and Curie temperature. The structural and magnetic properties of R,(Fe,Ti),, and R,(Fe,Ti),,N, depend on the kind of the rare-earth. The synthesis of single phase Ce,(Fe,Ti),, and Gd,(Fe,Ti),, samples, and the complete study of the crystallographic and magnetic properties of the series is in progress and will be published soon.
Acknowledgements This work was partially supported by the B/ECT91-405 project of the EU.
WI [I31 [I41 iI51 iI61 D71
[I81 [191 DO1 ml
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