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Magnetic properties of the intermetallic compounds Y15Fe77−xTxB8 (T = Mn, Co, Ni, x = 7, 17)
0038-1098/86 $3.00 + .00 Pergamon Press Ltd.
Solid State Communications, Vol. 57, No. 10, pp. 809-811, 1986. Printed in Great Britain.
MAGNETIC PROPERTIES OF THE INTERMETALLIC COMPOUNDS YlsFe77-xTxBs (T = Mn, Co, Ni, x = 7, 17) A. Szytuta and J. Drajewicz Institute of Physics, JageUonian University 30-059 Krak6w, Reymonta 4, Poland
(Received 23 August 1985; in revised form 18 October 1985 by E.F. Bertaut)
Magnetic properties of the compounds YzsFe77_xTxBa, where T stands for Mn, Co or Ni and x equals 7 or 17 were investigated within the temperature range 80 to 650 K. X-ray diffraction yielded a tetragonal structure of Nd2Fe14B type for all samples. The compounds appeared ferromagnetic: substitution of Mn or Ni for Fe leads to decrease of the Curie temperature and magnetization, while an increase of both quantities was observed for T = Co. 1. INTRODUCTION RECENT RESEARCH on rapidly quenched and heat treated alloys based on Fe and RE atoms has shown that giant coercivities and large energy products (BH)m can be obtained. Sagawa et al. [1] have shown that the phase RE2FeI4B is stable with RE = Nd to Tm and with Y. Herbst et al. [2] and Givord et al. [3] indicate that a new phase Nd2F%4B has tetragonal crystal structure. In this structure, Nd atoms are distributed on two crystallographic sites of low symmetry, whereas Fe atoms occupy six different sites. Magnetometric measurements indicate that Y2FeI4B is ferromagnetic with Curie temperature of 575 K [4]. According to Le Roux et al. [5], also Y2ColaB has tetragonal structure and ferromagnetic ordering with the Curie point of 1003 K. The present paper is concerned with the X-ray and magnetometric investigation of the YlsFe77_xTxBs system (T and x same as above), aimed at tracing changes that result from substituting of another 3d metal (Mn, Co, Ni) for Fe. 2. EXPERIMENT AND RESULTS The alloys were prepared from commercially available elements of high purity (Y - 3N, Mn, Fe, Co, Ni - 4N, B - 3N). Appropriate amounts of metals (proportional to the composition of the desired sample) were arc-melted in an argon atmosphere. The alloys were then given a post-sintering heat treatment for 1 h at 1250 K and cooled rapidly. X-ray diffraction studies on powdered samples (the Debye-Scherrer method) were carried out by means of the DRON-3 diffractometer operating with the FeKa radiation, at room temperature. All samples gave large 809
~,@
~
~
~ Co .~.
} Ni
1.3
1
1.1'95
1.190 .
'~
Q~1 "
~Z~
Fig. 1. Variation with concentration of the lattice constants, unit cell volumes and c/a ratios at room temperature. intensity Bragg reflections characteristic for the tetragonal Nd2Fe14B-type crystal structure, plus some additional small intensity lines of unknown origin. The least squares fit to the observed 20 values was used to obtain the lattice parameters. The latter are shown in Fig. 1. Substituting of Mn or Ni for Fe results in a decrease of the a and c constants, while substituting ot Co for Fe leads to the decrease of the c constant with simultaneous increase of the a constant. The lattice constants do not obey the Vegard's law. Magnetometric measurements were carried out
810
PROPERTIES OF THE INTERMETALLIC COMPOUNDS YlsFe77_xTxB8 ~'[cm3Gs l g
Vol. 57, No. 10
- r Arn2 1 L kg J
~°-
~..
z,C
I00
200
300
400
500
600
0
2
T[K]
4 H[T]
Fig. 2. Results of the magnetic measurements for the Y x s F e 7 7 _ x T x B 8 systems. 1 - YlsFe7TB8,2 - YlsFevoMnvBs, 3 - YlsFe6oMnlTBs, 4 - YlsFeToCovBs, 5 - YlsFe6oColvB8,6 - YlsFevoNi6B8,7 - YlsFe6oNilvB 8. between 80 and 650K, by means of an electronic balance, with the maximum field of IT. The magnetization a vs temperature curves are given in Fig. 2. All samples in question proved to be ferromagnetic. The corresponding Curie temperatures were derived from the a 2 vs temperature dependent obtained for H = 1T. At the liquid nitrogen temperature, the samples magnetization was studied in the fields up to 4T. The results are displayed in Fig. 2. The Curie temperature increases with increasing Co-concentration, but it decreases with increasing Ni concentration. For the Mn-containing compounds, a characteristic rapid decrease of the Curie temperature is observed with increasing Mn concentration. The magnetization of all samples was found to decrease while diluting the Fe sublattices (i.e. with increasing x). 3. DISCUSSION
150
~ Mn ~Co 100
~
Ni
iX
7o0" I----{
j ~ J
J
6t~
Tc[ K] 500~
30C
1
I
I
0
5
10
I
'
W
15
l
X 20
The compounds in question present a rather complicated tetragonal crystal structure of Nd2Fea4B type, in which the Fe atoms are distributed amongst its Fig. 3. Variation with concentration of the magnetization a and Curie temperatures Tc. six sublattices. Determination of whether there are any site preferences while diluting Fe was not possible due to It can be thus inferred that the atoms preserve the the very close values of X-rays scattering amplitudes for localized magnetic moment, but less than that of Fe Mn, Fe, Co and Ni. Such preferences do probably exist, (2.1 +0.1/aB) [4]. The picture changes, however, for as it can be expected from not fulfilling the Vegard's law T = Mn. The magnetization and the Curie temperaby a and c lattice constants as well as the cell volume. ture vary with the Mn concentration, x, for the Different directions of changes of lattice suggest in Y is Fe 77- xMnxB8 system much like for Y6(Fe 1- xMnx)23 particular that Co atoms take other sites than those of [7]. Rapid decrease of both quantities with increasing Mn concentration in both systems is caused by antiMn and Ni. Magnetic properties of the system investigated ferromagnetic coupling of the Fe and Mn magnetic do not significantly differ from those of other inter- moments. We learn from the referee report that analogous metallics of R E n T m type. [6] The F e - F e distance in a Nd2Fea4B-type structure varies between 0.24 and results have been obtained very recently (see [8] ). 0.28 nm [2] what suggests direct exchange interactions. A c k n o w l e d g e m e n t s - The authors would like to thank Both magnetization and the Curie temperature only Mr W. Zajac for useful discussion and editing the text slightly change while substituting Co and Ni for Fe. of this paper.
Vol. 57, No. 10
PROPERTIESOF THE INTERMETALLIC COMPOUNDS YlsFe77-xTxB8 REFERENCES
1.
M. Sagawa, S. Fujimura, M. Togawa, H. Yamamoto & Y. Matsuura, J. Appl. Phys. 55, 2083 (1984). J.F. Herbst, J.J. Croat, F.E. Pinkerton & W.B. 7. Yelon, Phys. Rev. B, 29, 4176 (1984). D. Givord, H.S. Li & J.M. Moreau, Solid State 8. Commun. 50,497 (1984). D. Givord, H.S. Li & R. Perrier de la Bathie, Solid State Commun. 51,857 (1984). D. Le Roux, H. Vincent, D. Fruchart, P. L'h6ritier ,
2. 3. 4. 5.
811
& R. Fruchart Extended Abstracts VIIIInt. Conf. of Solid Compounds of Transition Elements, Vienna P3 B6. (I985). H.R. Kirchmayer & C.A, Poldy, J. Magn. Magn. Mater. 8, 1 (1978). W.J. James K. Hardman, W. Yelon & B. Kebe, J. Phys. 40, C5 206 (1979). E. Burzo, E.B. Boltich, M.Q. Huang & W.E. Wallace, 8th Int. workshop on Rare Earth magnets and their applications, Dayton, USA, May 1985, 771-782.
Solid State Communications, Vol. 57, No. 10, pp. 809-811, 1986. Printed in Great Britain.
MAGNETIC PROPERTIES OF THE INTERMETALLIC COMPOUNDS YlsFe77-xTxBs (T = Mn, Co, Ni, x = 7, 17) A. Szytuta and J. Drajewicz Institute of Physics, JageUonian University 30-059 Krak6w, Reymonta 4, Poland
(Received 23 August 1985; in revised form 18 October 1985 by E.F. Bertaut)
Magnetic properties of the compounds YzsFe77_xTxBa, where T stands for Mn, Co or Ni and x equals 7 or 17 were investigated within the temperature range 80 to 650 K. X-ray diffraction yielded a tetragonal structure of Nd2Fe14B type for all samples. The compounds appeared ferromagnetic: substitution of Mn or Ni for Fe leads to decrease of the Curie temperature and magnetization, while an increase of both quantities was observed for T = Co. 1. INTRODUCTION RECENT RESEARCH on rapidly quenched and heat treated alloys based on Fe and RE atoms has shown that giant coercivities and large energy products (BH)m can be obtained. Sagawa et al. [1] have shown that the phase RE2FeI4B is stable with RE = Nd to Tm and with Y. Herbst et al. [2] and Givord et al. [3] indicate that a new phase Nd2F%4B has tetragonal crystal structure. In this structure, Nd atoms are distributed on two crystallographic sites of low symmetry, whereas Fe atoms occupy six different sites. Magnetometric measurements indicate that Y2FeI4B is ferromagnetic with Curie temperature of 575 K [4]. According to Le Roux et al. [5], also Y2ColaB has tetragonal structure and ferromagnetic ordering with the Curie point of 1003 K. The present paper is concerned with the X-ray and magnetometric investigation of the YlsFe77_xTxBs system (T and x same as above), aimed at tracing changes that result from substituting of another 3d metal (Mn, Co, Ni) for Fe. 2. EXPERIMENT AND RESULTS The alloys were prepared from commercially available elements of high purity (Y - 3N, Mn, Fe, Co, Ni - 4N, B - 3N). Appropriate amounts of metals (proportional to the composition of the desired sample) were arc-melted in an argon atmosphere. The alloys were then given a post-sintering heat treatment for 1 h at 1250 K and cooled rapidly. X-ray diffraction studies on powdered samples (the Debye-Scherrer method) were carried out by means of the DRON-3 diffractometer operating with the FeKa radiation, at room temperature. All samples gave large 809
~,@
~
~
~ Co .~.
} Ni
1.3
1
1.1'95
1.190 .
'~
Q~1 "
~Z~
Fig. 1. Variation with concentration of the lattice constants, unit cell volumes and c/a ratios at room temperature. intensity Bragg reflections characteristic for the tetragonal Nd2Fe14B-type crystal structure, plus some additional small intensity lines of unknown origin. The least squares fit to the observed 20 values was used to obtain the lattice parameters. The latter are shown in Fig. 1. Substituting of Mn or Ni for Fe results in a decrease of the a and c constants, while substituting ot Co for Fe leads to the decrease of the c constant with simultaneous increase of the a constant. The lattice constants do not obey the Vegard's law. Magnetometric measurements were carried out
810
PROPERTIES OF THE INTERMETALLIC COMPOUNDS YlsFe77_xTxB8 ~'[cm3Gs l g
Vol. 57, No. 10
- r Arn2 1 L kg J
~°-
~..
z,C
I00
200
300
400
500
600
0
2
T[K]
4 H[T]
Fig. 2. Results of the magnetic measurements for the Y x s F e 7 7 _ x T x B 8 systems. 1 - YlsFe7TB8,2 - YlsFevoMnvBs, 3 - YlsFe6oMnlTBs, 4 - YlsFeToCovBs, 5 - YlsFe6oColvB8,6 - YlsFevoNi6B8,7 - YlsFe6oNilvB 8. between 80 and 650K, by means of an electronic balance, with the maximum field of IT. The magnetization a vs temperature curves are given in Fig. 2. All samples in question proved to be ferromagnetic. The corresponding Curie temperatures were derived from the a 2 vs temperature dependent obtained for H = 1T. At the liquid nitrogen temperature, the samples magnetization was studied in the fields up to 4T. The results are displayed in Fig. 2. The Curie temperature increases with increasing Co-concentration, but it decreases with increasing Ni concentration. For the Mn-containing compounds, a characteristic rapid decrease of the Curie temperature is observed with increasing Mn concentration. The magnetization of all samples was found to decrease while diluting the Fe sublattices (i.e. with increasing x). 3. DISCUSSION
150
~ Mn ~Co 100
~
Ni
iX
7o0" I----{
j ~ J
J
6t~
Tc[ K] 500~
30C
1
I
I
0
5
10
I
'
W
15
l
X 20
The compounds in question present a rather complicated tetragonal crystal structure of Nd2Fea4B type, in which the Fe atoms are distributed amongst its Fig. 3. Variation with concentration of the magnetization a and Curie temperatures Tc. six sublattices. Determination of whether there are any site preferences while diluting Fe was not possible due to It can be thus inferred that the atoms preserve the the very close values of X-rays scattering amplitudes for localized magnetic moment, but less than that of Fe Mn, Fe, Co and Ni. Such preferences do probably exist, (2.1 +0.1/aB) [4]. The picture changes, however, for as it can be expected from not fulfilling the Vegard's law T = Mn. The magnetization and the Curie temperaby a and c lattice constants as well as the cell volume. ture vary with the Mn concentration, x, for the Different directions of changes of lattice suggest in Y is Fe 77- xMnxB8 system much like for Y6(Fe 1- xMnx)23 particular that Co atoms take other sites than those of [7]. Rapid decrease of both quantities with increasing Mn concentration in both systems is caused by antiMn and Ni. Magnetic properties of the system investigated ferromagnetic coupling of the Fe and Mn magnetic do not significantly differ from those of other inter- moments. We learn from the referee report that analogous metallics of R E n T m type. [6] The F e - F e distance in a Nd2Fea4B-type structure varies between 0.24 and results have been obtained very recently (see [8] ). 0.28 nm [2] what suggests direct exchange interactions. A c k n o w l e d g e m e n t s - The authors would like to thank Both magnetization and the Curie temperature only Mr W. Zajac for useful discussion and editing the text slightly change while substituting Co and Ni for Fe. of this paper.
Vol. 57, No. 10
PROPERTIESOF THE INTERMETALLIC COMPOUNDS YlsFe77-xTxB8 REFERENCES
1.
M. Sagawa, S. Fujimura, M. Togawa, H. Yamamoto & Y. Matsuura, J. Appl. Phys. 55, 2083 (1984). J.F. Herbst, J.J. Croat, F.E. Pinkerton & W.B. 7. Yelon, Phys. Rev. B, 29, 4176 (1984). D. Givord, H.S. Li & J.M. Moreau, Solid State 8. Commun. 50,497 (1984). D. Givord, H.S. Li & R. Perrier de la Bathie, Solid State Commun. 51,857 (1984). D. Le Roux, H. Vincent, D. Fruchart, P. L'h6ritier ,
2. 3. 4. 5.
811
& R. Fruchart Extended Abstracts VIIIInt. Conf. of Solid Compounds of Transition Elements, Vienna P3 B6. (I985). H.R. Kirchmayer & C.A, Poldy, J. Magn. Magn. Mater. 8, 1 (1978). W.J. James K. Hardman, W. Yelon & B. Kebe, J. Phys. 40, C5 206 (1979). E. Burzo, E.B. Boltich, M.Q. Huang & W.E. Wallace, 8th Int. workshop on Rare Earth magnets and their applications, Dayton, USA, May 1985, 771-782.