Journal of Alloys and Compounds 460 (2008) 1–7
Comparison of magnetic and transport properties of
Gd
6
YPd
3
and Gd
7
Pd
3
single crystals
Ewa Talik
∗
, Monika Klimczak, Robert Tro´ c, Joachim Kusz,
Wolfgang Hofmeister, Antoni Winiarski
Institute of Physics, Department of Solid State, Uniwersytecka 4, Katowice 40 007, Poland
Received 26 April 2007; received in revised form 14 May 2007; accepted 15 May 2007
Available online 18 May 2007
Abstract
Electronic structure, transport and magnetic properties of the Gd
6
YPd
3
single crystal have been measured. This compound crystallizes in the
hexagonal Th
7
Fe
3
type of structure with the ratio c/a = 0.63 similar to that obtained for Gd
7
Pd
3
. Gd
6
YPd
3
orders ferromagnetically at 299 K
while Gd
7
Pd
3
displays also ferromagnetic transition but at about 334K. All measured physical properties show a strong anisotropy. The thermal
dependence of the electrical resistivity shows an anomalous character having a strong negative curvature and quadratic temperature dependences
at low temperatures. The saturation magnetic moment per Gd ion is enhanced in relation to the theoretical value. Spin fluctuations taking place on
the palladium atoms may be responsible for the magnetic properties of ternary compound.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Rare earth-transition metal compounds; Single crystal; Electronic structure; Magnetocrystalline anisotropy
1. Introduction
Materials based on gadolinium are prospective for applica-
tions in magnetic refrigeration cycles. Recently, strong interest
has also been focused on the other magnetocaloric materials, like
as, e.g. RM
2
(M = Al, Co, Ni), MnFe(P
1-x
As
x
), Mn(As
1-x
Sb
x
)
and La(Fe
13-x
Si
x
) was reported [1,2]. Canepa et al. [3] found
the magnetocaloric effect for polycrystalline Gd
7
Pd
3
and fer-
romagnetic transition determined at T
C
= 323 K. Recently, a
wide investigation of the magnetic properties and tempera-
ture dependences of the lattice parameters of Gd
7
T
3
(T = Rh
and Pd) single crystals have been performed [4,5]. A strongly
anisotropic behaviour of the magnetic and transport properties
was observed. Moreover, there is a large difference between
the values of the ordering temperatures (T
C
= 334 K for Gd
7
Pd
3
and T
N
= 140 K for Gd
7
Rh
3
) and also in a type of the magnetic
ordering for both measured compounds, which crystallize in the
same type of the crystal structure with the same c/a ratio of 0.63.
Also, the complex character of the temperature dependence of
the lattice parameters of the Gd
7
T
3
was observed [5]. The aim
∗
Corresponding author. Tel.: +48 323591187; fax: +48 322588431.
E-mail address: talik@us.edu.pl (E. Talik).
of this work is to examine the influence on the magnetic prop-
erties of the obtained here Gd
6
YPd
3
due to the substitution of
non magnetic yttrium into the gadolinium sublattice.
2. Experimental
Single crystals of Gd
6
YPd
3
were obtained by the Czochralski method from a
levitated melt using high purity starting materials. The Berg–Barrett topography
confirmed that the obtained material was a single crystal (Fig. 1a and b).
The lattice parameters of a Gd
6
YPd
3
single crystal was estimated between
10 and 325 K, using a multilayer OSMIC monochromator with Cu K radi-
ation from a Schneider rotating anode and four-circle Huber diffractometer
with -circle in Mainz. The diffractometer was controlled by a STADI4 pro-
gram system and equipped with a two-stage closed-cycle helium-cooling device
(CTI-cryogenics). The temperature was controlled within 0.1 K.
The XPS spectra of the above single crystal were measured with monochro-
matized Al K radiation (1486.6 eV) at room temperature using a PHI 5700
ESCA spectrometer. The energy spectra of the electrons were determined by a
hemispherical mirror analyzer with an energy resolution of about 0.3eV.
The electrical resistivity measurements were performed on the single crystal
oriented parallel to all the principal crystallographic directions by a conven-
tional four probe method using 50 mA dc current in the temperature range 4.2–
300 K.
The dc magnetic susceptibility was measured using both the Faraday method
in a field of 900 Oe parallel to the a axis in the temperature range 4.2–800 K
under an atmosphere of helium. Magnetization was measured using a Quantum
Design MPMS SQUID magnetometer in the temperature range 1.9–400 K in
0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2007.05.057