- Email: [email protected]
Magnetic phase diagrams of UAsxSe1−x single crystals
Journal of Magnetism and Magnetic Materials 29 (1982) 291-296 North-Holland Publishing Company
291
MAGNETIC PHASE DIAGRAMS OF UAsxSel_ x SINGLE CRYSTALS
O. V O G T Laboratorium fiir FestkiJrperphysik, ETH, CH-8093 Ziirich, Switzerland
and H. B A R T H O L I N Service National des Champs Intenses 166X, F-38042 Grenoble Cedex, France, and Universitb de Toulon, F-83130 La Garde, France
Magnetization measurements as a function of temperature and concentration were performed on single crystals of the formula UAsxSe~-x- The results are summarized in magnetic phase diagrams.
1. Introduction
UAs is an antiferromagnet with a N6el temperature of 127 K [1]. Earlier neutron scattering experiments [1] performed on powdered samples revealed a phase transition at 66 K which was interpreted as a transition from type IA ( + + -- --) at low temperature to type I ( + - + - - ) antiferromagnetism with the spins along the cube axis of the NaC1 structure. Furthermore a 10% drop of the magnetic moment was reported but no plausible explanation was given. Recent experiments performed on single crystals [2] showed that the IA to I transition is accompanied by a transition from a 2 k (easy axis (110)) to a 1 k (easy axis (100)) collinear structure - thus explaning the change of the magnetic moment. The results agree with magnetization measurements mentioned below. Magnetic fields within the experimental range (100 kOe) induce an intermediate spin structure in UAs [3]. The type of this structure was investigated intensively with neutron scattering experiments [4,5] on single crystals. The results of such investigations can be summarized in "magnetic phase diagrams" i.e. diagrams splitting up the H-T space ( H - - - - m a g n e t i c field and T =
temperature) into isostructural regions. Examples of such diagrams are given below. Each critical point (either H or T) in magnetization versus applied-field curves (at fixed temperature) or magnetization versus temperature curves (at fixed applied fields) determines one point of a phase boundary in the H - T diagram. USe is a ferromagnet with a Curie temperature of 160 K [6]. The magnetization curves are extremely anisotropic - the (111) axis is the easy direction. Magnetizations measured along other axes are merely the projections on these directions of the magnetization confined along the (111) direction. Anisotropy is so strong that no rotation of the magnetization out of the (111) direction can be observed within the range of experimental fields. Anisotropy field must be in the region of megaoersteds. UAs and USe form a continuous series of mixed crystals UAsxSe ~ x all crystallizing with the NaC1 structure. These alloy systems are ideal for studying the transition from anti- to ferromagnetism. Such experiments were published years ago for powdered samples [7,8]. Our measurements, performed on single crystals, give more detailed resuits, revealing clearly the important phenomenon of strong anisotropy.
0304-8853/82/0000-0000/$02.75 © 1982 North-Holland
292
O. Vogt, H. Bartholin / Magnetic phase diagrams of UAsxSe I x single crystals
spin structures seem to be stabilized. At saturation the easy axis (maximum moment) is the <111> direction. Saturation moments along the other axes are the projections of the < 111 > moments on these axes, e.g. M < I O O > = 3 - i / 2 M ~ I I I > . The sample, which in its virgin state, is an antiferromagnet, becomes, once saturated, almost a ferromagnet. It is noteworthy, however, that the remanent magnetization along the < 111 > axis does not correspond to the full moment (about 10% lower) in contrast to the magnetizations along <110> and (100>. Thus, once magnetized, the sample is ferrimagnetic rather than ferromagnetic in zero field. At first sight it is difficult to judge whether the observed steps in the magnetization curves are due to intermediate spin structures or domain effects. (Neutron scattering experiments, of course, will give an unambiguous answer to this question.) One indication for the occurrence of intermediate spin structures is the fact that the corresponding moments are simple fractions (e.g. 1/3 or 2 / 3 ) of the full moment - pointing to rather simple kinds of intermediate structures). Another indication is the temperature dependence of the magnetization curve shown in fig. 2. Fig. 2 shows the complete hysteresis loop of the
2. Experimental Single crystals of UAsxSel -x (x : 1, 0.975, 0.95, 0.9, 0.8, 0.75, 0.7, 0.6, 0.5, 0.4) were grown by mineralization i.e. keeping pressed pellets of the desired composition in closed tungsten crucibles at about 50°C below the melting temperature for several weeks. This technique leads to crystals of at least 2 to 3 m m cube length. Magnetizations were measured by the moving-sample method either in a superconducting coil (100 kOe) or in a Bitter magnet (200 kOe) as a function of temperature (4.2 to 300 K).
3. Results Fig. 1 shows, on the typical example of UAs0.6Se0.4, some of the features encountered in m a g n e t i z a t i o n curves t h r o u g h the w h o l e UAsxSei x system. We have plotted the initial magnetization and magnetizations in subsequently decreasing ( H --, 0) fields (hysteresis loop). We note two very obvious facts: The magnetizations depend on the orientation of the applied field and as a function of increasing field; several intermediate
M
•
U As.6 Se 4
(pB)
T=42
20
K
_J_ < II0 )
.
.
.
.
.
.
.
.
.
~---
]
7"
I,
I0
(/,
I
I
50
60
(100>
.i,I t/
0
I0
20
50
40
70
810
H (kOe)
Fig. 1. Magnetizations of UAs0.6Se0. 4 (in magnetons per U-ion) versus applied field as a function of orientation at 4.2 K.
O. Vogt, H. Bartholin
/ Magnetic phase diagrams of UAsxSe I x single crystals
293
UAs ~Se~ UA~ 6Se 4
~,B) zo
/
(III) T:
/-
20K
#
T/
20
40
60
eO
a (kOe}
(110)
(iO0) ZOK
(i.)
/K ~111)
Fig. 2. Hysteresis loop of UAs0.6Se0.4 at 20 K along the easy axis. (ito) aOK
(100) 40~
same sample taken at 20 K along the easy axis. We note that the critical magnetic fields (i.e. fields required to induce an intermediate spin structure) are about 1/3 lower at 20 K compared to those at 4.2 K. The magnetic moments remain unchanged. The hysteresis field of the last step before saturation (which is 70 kOe at 4.2 K), however, is lowered to 20 kOe at 20 K. This is certainly a domain effect. On the other hand, we have strong evidence that all the other observed steps actually do correspond to intermediate phases. The complete hysteresis loop indicates that this sample is indeed a ferrimagnet (at H - - - 0 ) rather than a ferromagnet as one might guess by looking at the 4.2 K magnetization curves taken along the (100) or (110) axis (fig. 1). Due to strong anisotropy forces it can be very difficult to decide upon the nature of magnetic order in uranium compounds if only magnetization data are available. Fig. 3 shows typical examples of initial-magnetization curves for U m s 0 . 6 S e 0 . 4 both as a function of temperature and orientation of the applied field. On increasing the temperature the transition fields are generally lowered as is clearly visible. Obviously, thermal agitation facilitates the transition to new spin configurations. Therefore, in spite of the considerable differences found in the single magnetization curves, it is very well possible that the exchange forces do not depend on temperature. The anisotropy persists through the whole temperature range with the (111) direction remaining
(100) 60~
(ioo) llOK
~
(11o) 6OK
till) 40K
(tll) 6oK
(Ho) iio K
Fig. 3. Initial magnetization curves of UAs0.6Se0.4 versus applied field for different temperatures and orientations.
the easy axis. The magnetization curve for the (111 > direction at 110 K demonstrates quite clearly that great precautions are necessary in the interpretation of measurements - this curve looks indeed very much like measurements on an imperfect ferromagnet (powder measurements) although the sample is definitely ferrimagnetic. Information such as contained in fig. 3 can very elegantly be condensed in the form of a "magnetic phase diagram". Fig. 4 shows as an example the phase diagram of Ums0.975Se0.025.The H - T space is split up into isotructural regions. The phase diagram depends on the orientation of the applied field (it is different as well for increasing and decreasing fields). N o detailed pictures of the explicit spin structures
294
O. Vogt, H. Bartholin / Magnetic phase diagrams of UAsxSe t ~ single crystals
b o u n d a r i e s are f o u n d b y t h e r m o d y n a m i c considera t i o n a n d do therefore not d e p e n d o n a specific model. Extrapolating for H--, 0 we find the static case i.e. the different structures at zero field as a f u n c t i o n of temperature. We have s u m m a r i z e d our n u m e r o u s measurem e n t s for various samples in fig. 5. Small additions of Se to U A s increase the critical magnetic field below the IA to I transition a n d decrease these fields (to zero) above the IA to I transition which is, in turn, transferred towards higher temperatures. F o r x = 0.90 a n d x = 0.80 n o transition was observed over the whole temperature range even in fields of 200 kOe. T r a n s i t i o n s to ferri- a n d ferromagnetism set in again for x ~< 0.75. Finally, not shown in fig. 5, samples with x < 0.5 are ferromagnetic. I n fig. 6 we have plotted phase diagrams for H = 0 in the t e m p e r a t u r e ( T ) - c o n c e n t r a t i o n ( x )
UAs.gz5Se oz5
H (kOe)
2;
,50
..... •~ ~
~,~..
..........
(~nt>
/ ,L
//
,7 \ X
oo--,oo, W .... ~.-----...~:~,\
50
/..^_.\\
IA
/
\
I
,,,
~
,I,
50
I00
,I,,
T [K)I
,,
150
Fig. 4. Magnetic phase diagram of UAs0.975Se0.025 for 3 different orientations of the applied field.
are given ( d e n o m i n a t i o n s in fig. 4 are derived from a n a l o g y with the k n o w n phase d i a g r a m of UAs) b y m a g n e t i z a t i o n measurements. The observed
H (kOe) 150
UAs
/C~
H [kOe)
_ Ik-~erri
H 11
UAsr~e,z5
f5C
2 ~ - ferri
IOC
IOC
fem 2k
50
pe o
0
5(
C
UAs 7Se3
UAs.9~Se.o25 150
H Jl
(100)
-
t5(
2 k- fer ri
fe~i
I k -ferri
ferro
I00
~0( fe
50
yp
pero
5(
I
Type I
(
0
UAs.6Se4
UAs.95Se.o5 150
H
If
(100~*
15q
2~ferrl
I
I00
I OI
50
5
ferro
25
50
75
I00
125 T ( K
C
0
25
50
7'5
100
125 T ( K )
Fig. 5. Magnetic phase diagrams of several UAsxSe1 ., compounds. H along the 100 axis.
295
O. Vogt, H. Bartholin / Magnetic phase diagrams of (-/Asx Se I - x single crystals
UAsxSe,_x
UAsx Se ,-x
/
(100) H.O
I I I I I
pom
mod
I I J ferm
I00
fern mcNmsir~ JP
moment
ferro
IA
~0
---t-
%
g.
g.
o'.
o.
o~ ,~,
04
tO
09
O.e
07
06
OS
IX)
04
Fig. 6. Suggested phase diagrams of UAs,Se I x for H =0. Left: after Obolenski and Troc [7] - right: this work.
space, On the left side we reproduce the diagram suggested by Obolenski and Tro6 [7], the right side is based on our own magnetic measurements (extrapolation H - ~ 0 in the phase diagrams). The transition to ferromagnetism with decreasing x does not occur by lowering of the critical fields. The actual transition is a stepwise increase of the ferrimagnetic moment.
4. Conclusions As the most important and unexpected result of our investigation of the pseudobinary system U A s x S e l _ x we notice that no direct transition from antiferromagnetism to ferromagnetism occurs at any point of the H, T, x space. More detailed studies with neutrons and a subsequent analysis of the exchange and anisotropy forces might give a convincing explanation for this behaviour.
Acknowledgements The authors are very grateful to Prof. Aubert of S N C I Grenoble for the permission of performing the measurements in static dc fields in his laboratories. This work was financially supported by the Swiss National Science Foundation. The skilful technical assistance of Messrs. K. Mattenberger and L. Scherrer in growing crystals and performing the measurements is gratefully acknowledged.
References
[1] D.I. Lain and A.T. Aldred, The Actinides: Electronic Structure and Related Properties, eds. A.J. Freeman and J.D. Darby (Academic Press, New York, 1974) p. 131. [2] J. Rossat-Mignod, P. Burlet, S. Quezel and O. Vogt, Physica 102B (1980) 237.
296
O. Vogt, H. Bartholin / Magnetic phase diagrams of UAsxSe l_ X single crystals
[3] G. Busch, O. Vogt and H. Bartholin, J. de Phys. C4-40 (1979) 64. [4] S.K. Sinha, G.H. Lander, S.M. Shapiro and O. Vogt, Phys: Rev. B23 (1981) 4556. [5] J. Rossat-Mignod, P. Burlet, H. Bartholin, R. Tchapoutian, O. Vogt, C. Vettier and R. Lagnier, Physica 102B (1980) 177.
[6] G. Busch and O. Vogt, J. Less-Common Metals 62 (1978) 335. [7] M. Obolenski and R. Tro6, Proc. 2nd Int. Conf. Electr. Structure Actinides Wroclaw (1976) p. 397. [8] J. Leciejewicz, R. Troc, A. Murasik and T. Palewski, Phys. Stat. Sol. (b) 48 (1971) 445.
291
MAGNETIC PHASE DIAGRAMS OF UAsxSel_ x SINGLE CRYSTALS
O. V O G T Laboratorium fiir FestkiJrperphysik, ETH, CH-8093 Ziirich, Switzerland
and H. B A R T H O L I N Service National des Champs Intenses 166X, F-38042 Grenoble Cedex, France, and Universitb de Toulon, F-83130 La Garde, France
Magnetization measurements as a function of temperature and concentration were performed on single crystals of the formula UAsxSe~-x- The results are summarized in magnetic phase diagrams.
1. Introduction
UAs is an antiferromagnet with a N6el temperature of 127 K [1]. Earlier neutron scattering experiments [1] performed on powdered samples revealed a phase transition at 66 K which was interpreted as a transition from type IA ( + + -- --) at low temperature to type I ( + - + - - ) antiferromagnetism with the spins along the cube axis of the NaC1 structure. Furthermore a 10% drop of the magnetic moment was reported but no plausible explanation was given. Recent experiments performed on single crystals [2] showed that the IA to I transition is accompanied by a transition from a 2 k (easy axis (110)) to a 1 k (easy axis (100)) collinear structure - thus explaning the change of the magnetic moment. The results agree with magnetization measurements mentioned below. Magnetic fields within the experimental range (100 kOe) induce an intermediate spin structure in UAs [3]. The type of this structure was investigated intensively with neutron scattering experiments [4,5] on single crystals. The results of such investigations can be summarized in "magnetic phase diagrams" i.e. diagrams splitting up the H-T space ( H - - - - m a g n e t i c field and T =
temperature) into isostructural regions. Examples of such diagrams are given below. Each critical point (either H or T) in magnetization versus applied-field curves (at fixed temperature) or magnetization versus temperature curves (at fixed applied fields) determines one point of a phase boundary in the H - T diagram. USe is a ferromagnet with a Curie temperature of 160 K [6]. The magnetization curves are extremely anisotropic - the (111) axis is the easy direction. Magnetizations measured along other axes are merely the projections on these directions of the magnetization confined along the (111) direction. Anisotropy is so strong that no rotation of the magnetization out of the (111) direction can be observed within the range of experimental fields. Anisotropy field must be in the region of megaoersteds. UAs and USe form a continuous series of mixed crystals UAsxSe ~ x all crystallizing with the NaC1 structure. These alloy systems are ideal for studying the transition from anti- to ferromagnetism. Such experiments were published years ago for powdered samples [7,8]. Our measurements, performed on single crystals, give more detailed resuits, revealing clearly the important phenomenon of strong anisotropy.
0304-8853/82/0000-0000/$02.75 © 1982 North-Holland
292
O. Vogt, H. Bartholin / Magnetic phase diagrams of UAsxSe I x single crystals
spin structures seem to be stabilized. At saturation the easy axis (maximum moment) is the <111> direction. Saturation moments along the other axes are the projections of the < 111 > moments on these axes, e.g. M < I O O > = 3 - i / 2 M ~ I I I > . The sample, which in its virgin state, is an antiferromagnet, becomes, once saturated, almost a ferromagnet. It is noteworthy, however, that the remanent magnetization along the < 111 > axis does not correspond to the full moment (about 10% lower) in contrast to the magnetizations along <110> and (100>. Thus, once magnetized, the sample is ferrimagnetic rather than ferromagnetic in zero field. At first sight it is difficult to judge whether the observed steps in the magnetization curves are due to intermediate spin structures or domain effects. (Neutron scattering experiments, of course, will give an unambiguous answer to this question.) One indication for the occurrence of intermediate spin structures is the fact that the corresponding moments are simple fractions (e.g. 1/3 or 2 / 3 ) of the full moment - pointing to rather simple kinds of intermediate structures). Another indication is the temperature dependence of the magnetization curve shown in fig. 2. Fig. 2 shows the complete hysteresis loop of the
2. Experimental Single crystals of UAsxSel -x (x : 1, 0.975, 0.95, 0.9, 0.8, 0.75, 0.7, 0.6, 0.5, 0.4) were grown by mineralization i.e. keeping pressed pellets of the desired composition in closed tungsten crucibles at about 50°C below the melting temperature for several weeks. This technique leads to crystals of at least 2 to 3 m m cube length. Magnetizations were measured by the moving-sample method either in a superconducting coil (100 kOe) or in a Bitter magnet (200 kOe) as a function of temperature (4.2 to 300 K).
3. Results Fig. 1 shows, on the typical example of UAs0.6Se0.4, some of the features encountered in m a g n e t i z a t i o n curves t h r o u g h the w h o l e UAsxSei x system. We have plotted the initial magnetization and magnetizations in subsequently decreasing ( H --, 0) fields (hysteresis loop). We note two very obvious facts: The magnetizations depend on the orientation of the applied field and as a function of increasing field; several intermediate
M
•
U As.6 Se 4
(pB)
T=42
20
K
_J_ < II0 )
.
.
.
.
.
.
.
.
.
~---
]
7"
I,
I0
(/,
I
I
50
60
(100>
.i,I t/
0
I0
20
50
40
70
810
H (kOe)
Fig. 1. Magnetizations of UAs0.6Se0. 4 (in magnetons per U-ion) versus applied field as a function of orientation at 4.2 K.
O. Vogt, H. Bartholin
/ Magnetic phase diagrams of UAsxSe I x single crystals
293
UAs ~Se~ UA~ 6Se 4
~,B) zo
/
(III) T:
/-
20K
#
T/
20
40
60
eO
a (kOe}
(110)
(iO0) ZOK
(i.)
/K ~111)
Fig. 2. Hysteresis loop of UAs0.6Se0.4 at 20 K along the easy axis. (ito) aOK
(100) 40~
same sample taken at 20 K along the easy axis. We note that the critical magnetic fields (i.e. fields required to induce an intermediate spin structure) are about 1/3 lower at 20 K compared to those at 4.2 K. The magnetic moments remain unchanged. The hysteresis field of the last step before saturation (which is 70 kOe at 4.2 K), however, is lowered to 20 kOe at 20 K. This is certainly a domain effect. On the other hand, we have strong evidence that all the other observed steps actually do correspond to intermediate phases. The complete hysteresis loop indicates that this sample is indeed a ferrimagnet (at H - - - 0 ) rather than a ferromagnet as one might guess by looking at the 4.2 K magnetization curves taken along the (100) or (110) axis (fig. 1). Due to strong anisotropy forces it can be very difficult to decide upon the nature of magnetic order in uranium compounds if only magnetization data are available. Fig. 3 shows typical examples of initial-magnetization curves for U m s 0 . 6 S e 0 . 4 both as a function of temperature and orientation of the applied field. On increasing the temperature the transition fields are generally lowered as is clearly visible. Obviously, thermal agitation facilitates the transition to new spin configurations. Therefore, in spite of the considerable differences found in the single magnetization curves, it is very well possible that the exchange forces do not depend on temperature. The anisotropy persists through the whole temperature range with the (111) direction remaining
(100) 60~
(ioo) llOK
~
(11o) 6OK
till) 40K
(tll) 6oK
(Ho) iio K
Fig. 3. Initial magnetization curves of UAs0.6Se0.4 versus applied field for different temperatures and orientations.
the easy axis. The magnetization curve for the (111 > direction at 110 K demonstrates quite clearly that great precautions are necessary in the interpretation of measurements - this curve looks indeed very much like measurements on an imperfect ferromagnet (powder measurements) although the sample is definitely ferrimagnetic. Information such as contained in fig. 3 can very elegantly be condensed in the form of a "magnetic phase diagram". Fig. 4 shows as an example the phase diagram of Ums0.975Se0.025.The H - T space is split up into isotructural regions. The phase diagram depends on the orientation of the applied field (it is different as well for increasing and decreasing fields). N o detailed pictures of the explicit spin structures
294
O. Vogt, H. Bartholin / Magnetic phase diagrams of UAsxSe t ~ single crystals
b o u n d a r i e s are f o u n d b y t h e r m o d y n a m i c considera t i o n a n d do therefore not d e p e n d o n a specific model. Extrapolating for H--, 0 we find the static case i.e. the different structures at zero field as a f u n c t i o n of temperature. We have s u m m a r i z e d our n u m e r o u s measurem e n t s for various samples in fig. 5. Small additions of Se to U A s increase the critical magnetic field below the IA to I transition a n d decrease these fields (to zero) above the IA to I transition which is, in turn, transferred towards higher temperatures. F o r x = 0.90 a n d x = 0.80 n o transition was observed over the whole temperature range even in fields of 200 kOe. T r a n s i t i o n s to ferri- a n d ferromagnetism set in again for x ~< 0.75. Finally, not shown in fig. 5, samples with x < 0.5 are ferromagnetic. I n fig. 6 we have plotted phase diagrams for H = 0 in the t e m p e r a t u r e ( T ) - c o n c e n t r a t i o n ( x )
UAs.gz5Se oz5
H (kOe)
2;
,50
..... •~ ~
~,~..
..........
(~nt>
/ ,L
//
,7 \ X
oo--,oo, W .... ~.-----...~:~,\
50
/..^_.\\
IA
/
\
I
,,,
~
,I,
50
I00
,I,,
T [K)I
,,
150
Fig. 4. Magnetic phase diagram of UAs0.975Se0.025 for 3 different orientations of the applied field.
are given ( d e n o m i n a t i o n s in fig. 4 are derived from a n a l o g y with the k n o w n phase d i a g r a m of UAs) b y m a g n e t i z a t i o n measurements. The observed
H (kOe) 150
UAs
/C~
H [kOe)
_ Ik-~erri
H 11
UAsr~e,z5
f5C
2 ~ - ferri
IOC
IOC
fem 2k
50
pe o
0
5(
C
UAs 7Se3
UAs.9~Se.o25 150
H Jl
(100)
-
t5(
2 k- fer ri
fe~i
I k -ferri
ferro
I00
~0( fe
50
yp
pero
5(
I
Type I
(
0
UAs.6Se4
UAs.95Se.o5 150
H
If
(100~*
15q
2~ferrl
I
I00
I OI
50
5
ferro
25
50
75
I00
125 T ( K
C
0
25
50
7'5
100
125 T ( K )
Fig. 5. Magnetic phase diagrams of several UAsxSe1 ., compounds. H along the 100 axis.
295
O. Vogt, H. Bartholin / Magnetic phase diagrams of (-/Asx Se I - x single crystals
UAsxSe,_x
UAsx Se ,-x
/
(100) H.O
I I I I I
pom
mod
I I J ferm
I00
fern mcNmsir~ JP
moment
ferro
IA
~0
---t-
%
g.
g.
o'.
o.
o~ ,~,
04
tO
09
O.e
07
06
OS
IX)
04
Fig. 6. Suggested phase diagrams of UAs,Se I x for H =0. Left: after Obolenski and Troc [7] - right: this work.
space, On the left side we reproduce the diagram suggested by Obolenski and Tro6 [7], the right side is based on our own magnetic measurements (extrapolation H - ~ 0 in the phase diagrams). The transition to ferromagnetism with decreasing x does not occur by lowering of the critical fields. The actual transition is a stepwise increase of the ferrimagnetic moment.
4. Conclusions As the most important and unexpected result of our investigation of the pseudobinary system U A s x S e l _ x we notice that no direct transition from antiferromagnetism to ferromagnetism occurs at any point of the H, T, x space. More detailed studies with neutrons and a subsequent analysis of the exchange and anisotropy forces might give a convincing explanation for this behaviour.
Acknowledgements The authors are very grateful to Prof. Aubert of S N C I Grenoble for the permission of performing the measurements in static dc fields in his laboratories. This work was financially supported by the Swiss National Science Foundation. The skilful technical assistance of Messrs. K. Mattenberger and L. Scherrer in growing crystals and performing the measurements is gratefully acknowledged.
References
[1] D.I. Lain and A.T. Aldred, The Actinides: Electronic Structure and Related Properties, eds. A.J. Freeman and J.D. Darby (Academic Press, New York, 1974) p. 131. [2] J. Rossat-Mignod, P. Burlet, S. Quezel and O. Vogt, Physica 102B (1980) 237.
296
O. Vogt, H. Bartholin / Magnetic phase diagrams of UAsxSe l_ X single crystals
[3] G. Busch, O. Vogt and H. Bartholin, J. de Phys. C4-40 (1979) 64. [4] S.K. Sinha, G.H. Lander, S.M. Shapiro and O. Vogt, Phys: Rev. B23 (1981) 4556. [5] J. Rossat-Mignod, P. Burlet, H. Bartholin, R. Tchapoutian, O. Vogt, C. Vettier and R. Lagnier, Physica 102B (1980) 177.
[6] G. Busch and O. Vogt, J. Less-Common Metals 62 (1978) 335. [7] M. Obolenski and R. Tro6, Proc. 2nd Int. Conf. Electr. Structure Actinides Wroclaw (1976) p. 397. [8] J. Leciejewicz, R. Troc, A. Murasik and T. Palewski, Phys. Stat. Sol. (b) 48 (1971) 445.