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Polarisation analysis measurements on mixed phase Pd1.4Cu0.6MnIn
Journal of Magnetism and Magnetic Materials 31-34 (1983) 623-624 POLARISATION P.J. W E B S T E R
ANALYSIS
623
MEASUREMENTS
and K.R.A. ZIEBECK
ON MIXED PHASE
P d t.4Cua.6 M n l n
*
Department qf Pure and Applied Physics, University of Salford, Salford M5 4WT, England
The magnetic moment in the mixed magnetic intermetallic compound Pdl.4Cu0.6Mnln has been determined using polarisation analysis measurements in the paramagnetic phase. The data show no evidence of spatial correlations and indicate a localised moment of 4.15#n and are well represented by the Watson and Freeman 3d Mn 2+ form factor.
1. Introduction
Intermetallic compounds in the P d 2 _ x C u x M n l n system have the L21 (Heusler) structure shown in fig. 1, with the P d / C u atoms randomly occupying the cube centre sites and the Mn and In atoms ordered alternately on the cube corner sites [1]. The magnetic structures are similar to those found in the P d 2 M n l n t_xSnx system [2]. They vary with conduction electron concentration from antiferromagnetic fcc type 2 at the palladium rich end to fcc type 3A and then ferromagnetism as the copper concentration is increased. Between the regions of single magnetic phase, mixed magnetic phase regions appear to co-exist. The intermetallic c o m p o u n d Pd 1.4Cu0.6Mnln is typical of the mixed magnetic phase alloys. It is largely ferromagnetic with a Curie temperature 170 K with the remainder fcc type 3A together with a small residual amount of fcc type 2. Results are presented here of magnetic and neutron diffraction measurements made on the representative intermetallic compound PdL4Cu0.6Mnln in order to obtain the size of the magnetic moment, to enable the magnetic structures to be determined, and to investigate the spatial correlations.
-- 30 '-~. E *' 20 ~lO
26o
100 60 E --- 20
b 100
200
300
~00
500
Temperoture (K)
Fig. 2, (a) Spontaneous magnetisation MOT; (b) reciprocal susceptibility versus temperature.
2. Experimental
A 30 g sample of Pdl.4Cu0.6Mnln was prepared by melting the appropriate quantities of 4n constituent elements in an argon arc furnace. The weight loss was t,00
e, ~200
Pd/Cu Hn In Fig. 1. The Heusler (L21 type) structure. * Institut Laue-Langevin, 156X Centre de Tri, 38042 Grenoble Cedex, France. 0304-8853/0000-0000/$03.00
© 1983 N o r t h - H o l l a n d
i
I
1
i
~
I
Q (A-7)
*
3
Fig. 3. Neutron counts (spin up-spin down) versus wave vector Q = (4~t sin 0)/X.
624
P.J. Webster, K.R.A. Ziebeck / Polarisation analysis of Pd l.4Cuo.r Mnln
6
2
Fig. 4. Paf versus Q corrected for the calculated 3d Mn2+ form factor.
1.2% on melting. Specimens for magnetic analysis were cut from the ingot and the remainder was crushed to a particle size of less than 250 /~m. The samples for magnetic analysis were ground to the shape of approximate ellipsoids before being sealed with the powder in a quartz ampoule under a reduced inert gas atmosphere. The sample was annealed for two days at 800°C followed by a slow cool to room temperature over five days. An X-ray powder diffraction photograph indicated a single phase structure of the Heusler type with a lattice parameter 6.337/k. Bulk magnetisation and susceptibility measurements were made at temperatures between 4.2 and 500 K at a series of applied fields up to 15 kOe. The results are shown in fig. 2 and indicate a Curie temperature of 170 K and a saturation moment/~00 = 2.36/xB, from the ferromagnetic data, but a moment of 4.1#B from the susceptibility data. Neutron diffraction powder diffraction measurements were made at AERE, Harwell using the Curran diffractometer at 4.2 K. The pattern showed strong antiferromagnetic fcc type 3A, weak fcc type 2 reflections and ferromagnetic contributions to the fcc reflections. The intensities were compatible with 55% ferro-
magnetism, 40% type 3A and 5% type 2 with a moment of 4.1/~ in good agreement with the magnetic data. Polarisation analysis measurements were made on the same powder sample, at room temperature in the paramagnetic phase, using the D5 diffractometer at ILL, Grenoble. The results are shown in figs. 3 and 4. Details of the experimental techniques used have been described by Ziebeck et al. [3]. 3. Discussion
The solid line in fig. 3 shows the square of the Mn 2+ 3d form factor calculated by Watson and Freeman [4] and scaled to fit the data. Fig. 4 shows Pelf obtained from the data, taking into account the form factor and normalizing against the (111), (200) and (220) Bragg reflections. The response is flat with no wave vector dependence and Pelf = 5.05/tB equivalent to a localised 3d moment of 4.15/xB in agreement with the low temperature neutron diffraction and magnetic data. There is no evidence of any spatial correlations and the data are well represented by the Watson and Freeman Mn 2+ form factor. We would like to thank R.M. Mankikar for making the neutron diffraction measurements at Harwell and the magnetic measurements, and A. Perkins for his assistance with the D5 measurements at ILL. References
[1] P.J. Webster, J. Appl. Phys. 52 (1981) 2040. [2] P.J. Webster and M.R.I. Ramadan, J. Magn. Magn. Mat. 13 (1977) 51. [3] K.R.A. Ziebeek, P.J. Webster, P.J. Brown and J.A.C. Bland, J. Magn. Magn. Mat. 24 (1981) 258. [4] A.J. Freeman and R.E. Watson, Acta. Cryst. 14 (1961) 231.
ANALYSIS
623
MEASUREMENTS
and K.R.A. ZIEBECK
ON MIXED PHASE
P d t.4Cua.6 M n l n
*
Department qf Pure and Applied Physics, University of Salford, Salford M5 4WT, England
The magnetic moment in the mixed magnetic intermetallic compound Pdl.4Cu0.6Mnln has been determined using polarisation analysis measurements in the paramagnetic phase. The data show no evidence of spatial correlations and indicate a localised moment of 4.15#n and are well represented by the Watson and Freeman 3d Mn 2+ form factor.
1. Introduction
Intermetallic compounds in the P d 2 _ x C u x M n l n system have the L21 (Heusler) structure shown in fig. 1, with the P d / C u atoms randomly occupying the cube centre sites and the Mn and In atoms ordered alternately on the cube corner sites [1]. The magnetic structures are similar to those found in the P d 2 M n l n t_xSnx system [2]. They vary with conduction electron concentration from antiferromagnetic fcc type 2 at the palladium rich end to fcc type 3A and then ferromagnetism as the copper concentration is increased. Between the regions of single magnetic phase, mixed magnetic phase regions appear to co-exist. The intermetallic c o m p o u n d Pd 1.4Cu0.6Mnln is typical of the mixed magnetic phase alloys. It is largely ferromagnetic with a Curie temperature 170 K with the remainder fcc type 3A together with a small residual amount of fcc type 2. Results are presented here of magnetic and neutron diffraction measurements made on the representative intermetallic compound PdL4Cu0.6Mnln in order to obtain the size of the magnetic moment, to enable the magnetic structures to be determined, and to investigate the spatial correlations.
-- 30 '-~. E *' 20 ~lO
26o
100 60 E --- 20
b 100
200
300
~00
500
Temperoture (K)
Fig. 2, (a) Spontaneous magnetisation MOT; (b) reciprocal susceptibility versus temperature.
2. Experimental
A 30 g sample of Pdl.4Cu0.6Mnln was prepared by melting the appropriate quantities of 4n constituent elements in an argon arc furnace. The weight loss was t,00
e, ~200
Pd/Cu Hn In Fig. 1. The Heusler (L21 type) structure. * Institut Laue-Langevin, 156X Centre de Tri, 38042 Grenoble Cedex, France. 0304-8853/0000-0000/$03.00
© 1983 N o r t h - H o l l a n d
i
I
1
i
~
I
Q (A-7)
*
3
Fig. 3. Neutron counts (spin up-spin down) versus wave vector Q = (4~t sin 0)/X.
624
P.J. Webster, K.R.A. Ziebeck / Polarisation analysis of Pd l.4Cuo.r Mnln
6
2
Fig. 4. Paf versus Q corrected for the calculated 3d Mn2+ form factor.
1.2% on melting. Specimens for magnetic analysis were cut from the ingot and the remainder was crushed to a particle size of less than 250 /~m. The samples for magnetic analysis were ground to the shape of approximate ellipsoids before being sealed with the powder in a quartz ampoule under a reduced inert gas atmosphere. The sample was annealed for two days at 800°C followed by a slow cool to room temperature over five days. An X-ray powder diffraction photograph indicated a single phase structure of the Heusler type with a lattice parameter 6.337/k. Bulk magnetisation and susceptibility measurements were made at temperatures between 4.2 and 500 K at a series of applied fields up to 15 kOe. The results are shown in fig. 2 and indicate a Curie temperature of 170 K and a saturation moment/~00 = 2.36/xB, from the ferromagnetic data, but a moment of 4.1#B from the susceptibility data. Neutron diffraction powder diffraction measurements were made at AERE, Harwell using the Curran diffractometer at 4.2 K. The pattern showed strong antiferromagnetic fcc type 3A, weak fcc type 2 reflections and ferromagnetic contributions to the fcc reflections. The intensities were compatible with 55% ferro-
magnetism, 40% type 3A and 5% type 2 with a moment of 4.1/~ in good agreement with the magnetic data. Polarisation analysis measurements were made on the same powder sample, at room temperature in the paramagnetic phase, using the D5 diffractometer at ILL, Grenoble. The results are shown in figs. 3 and 4. Details of the experimental techniques used have been described by Ziebeck et al. [3]. 3. Discussion
The solid line in fig. 3 shows the square of the Mn 2+ 3d form factor calculated by Watson and Freeman [4] and scaled to fit the data. Fig. 4 shows Pelf obtained from the data, taking into account the form factor and normalizing against the (111), (200) and (220) Bragg reflections. The response is flat with no wave vector dependence and Pelf = 5.05/tB equivalent to a localised 3d moment of 4.15/xB in agreement with the low temperature neutron diffraction and magnetic data. There is no evidence of any spatial correlations and the data are well represented by the Watson and Freeman Mn 2+ form factor. We would like to thank R.M. Mankikar for making the neutron diffraction measurements at Harwell and the magnetic measurements, and A. Perkins for his assistance with the D5 measurements at ILL. References
[1] P.J. Webster, J. Appl. Phys. 52 (1981) 2040. [2] P.J. Webster and M.R.I. Ramadan, J. Magn. Magn. Mat. 13 (1977) 51. [3] K.R.A. Ziebeek, P.J. Webster, P.J. Brown and J.A.C. Bland, J. Magn. Magn. Mat. 24 (1981) 258. [4] A.J. Freeman and R.E. Watson, Acta. Cryst. 14 (1961) 231.