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Normal-state Hall effect in c-axis and a-axis oriented EuBa2Cu3O7 superconducting thin films
PHYSlCA ELSEVIER
Physica B 199&200 (1994) 246-247
Normal-state Hall effect in c-axis and a-axis oriented EuBa2Cu307 superconducting thin films J. Colino ~, J.l. Martiia b, J.L. Vicent b'* '~blstituto tte Ciem'ia tit, Materiales. C.S.L C. Serrano 144. MadrM 28006, Spai:~ Dcpartamento de Fisica de Materiales, Facuhad &, Fish'as. Unit,ersidad Comph~tense, Ciudad Universitaria s/n, MadrM 28040, Spain
Abstract Thin films of EuBa2Cu~O~ were obtained by DC magnetron sputtering on SrTiO3(1 0 0). The substrate temperature allows us to grow c-axis oriented ( ,-, 800 °C) or a-axis oriented ( ,.~ 680'~C) films. The DC four-sweep method was used to measure the Hall angle (0n) of patterned films between 100 and 250 K with applied magnetic fields up to 90 kOe. Samples with c-axis texture show ctg0H with the typical -,, T 2 behavior. In t 'rn, samples with a-axis orientation (H IIa-axis) show a negative Hall signal and ctg 0.d T) does not extrapolate to zero.
I. introduction
2. Experimental
The normal-state Hall effect of (RE)BaaCu~O7 superconducting cuprates has been extensively studied, for instance, as a function of temperature [1 4] and oxygen deficiency I-5,6]. In most of these works the magnetic field is perpendicular to the CuO2 planes (Hx), whereas the parallel field geometry (H 0 has scarcely been reported I1, 3]. The Hall coefficient (RH) is positive (holelike) in the Hi_ geometry, On the other hand, Rn is negative when both the current and magnetic field are parallel (H~) to the CuO2 planes. Thin films are very suitable for the Hall effect geometric requirements. However, the few reports of the Hti-Hail effect have been done in crystals. This fact arises from the usual c-axis orientation of the i :2:3 films. As far as we know there is only one previous report on the Hall coefficient of a-axis films [7_]. In this paper we report on the resistivity and Hall measurements of pure a-axis oriented and pure c-axis oriented thin films in the normal state.
Pure a-axis and pure c-axis oriented thin films have been grown by DC magnetron sputtering using the NACHOS technique I-8]. The details of sample preparation have been published elsewhere [9]. X-ray diffraction (Cu K,) shows the unique orientation (c- or a-axis perpendicular to the substrate) of our films on SrTiO3 (! 00),The patterned Hall bars exhibit narrow superconducting transition: ~ 2 K in c-axis films and ~ 4 K in a-axis films. A commercial 90 kOe supercond',zting solenoid, w~th H always lying perpendicular to the sut~strate, was used for the Hall measmements.
* Corresponding attthor.
3. Resuhs and discussion Figure 1 and the inset show the Hall resistivity and longitudinal resistivity, respectively, for pure a-axis films, pure c-axis films and mixed oriented a + c films. It can be seen that the resistivity P.,x of pucc c-axis and mixed a + c oriented films I "-- 5% c-orientation) is linear in
(P~21-4526 94.$07.00 ~) 1994 Elsevier Science B.V. All rights reserved S~DI 0921-4526(93)E0215-3
1. Cohn
0
100200300
c*-
T(K)
9 -=
-
1
QX
dC o _,&L/;.“.“‘” 1L.
cc
ce
cl al. / PIysica
/=
cc
40
-
... ..f,,...,...... ..,. _,__.... ..“” ,.._.._....
----_ _._
---__
---.____
.
-1 2
0
4
6
8
1c
H(T) Fig. I. Hall resistivity
versus magnetic field at -
100 K for pure
c-axis films (dashed line), pure a-axis films (solid line) and mixed a + c
films (dotted
temperature
line). The inset shows the resistivity
versus
of the same films.
B I99&200
( 19941
?4b -247
247
Bragg scans. Since we measure a-axis films with no trace of (001) reflections, the negative RH is an intrinsic property of 1: 2: 3 films in H,, geometry. From the Hall coefficient at + 100 K we can estimate, in a free electron model, a number of carriers per unit cell of the order of 1.6 ( - ) in cl-axis films and 0.5 ( + ) in c-axis films. These values are very close to those of single crystals [ 1,3]. The rtg& ( = pxx/p,) of c-axis films (Fig. 2) shows a - T2 behavior, similar to that previously reported [l-6]. a-axis oriented films have a rather insensitive temperature dependence of l/R” (see the inset of Fig. 2). The fact that these experiments have been done in patterned thin films rules out a possible influence of sample shape in the Hall measurement. The ctg& of a-axis films does not extrapolate to zero at low temperatures, rather it slightly changes with temperature. In summary, we have measured the Hall angle of pure c-axis oriented films, pure a-axis oriented films and mixed a + c oriented films. In pure a-axis films R,,(HI(a) - - 6101-‘~ m”/C agrees with previous single crystal data [ 1,3]. We have also shown that small amounts of c-axis orientation drastically change the If,,Hall coefficient, even turning to hole-like conduction. In contrast to the behavior of the Hall angle in c-axis films. both RH and ctg Onof a-axis films are rather insensitive to temperature. This point is not yet clearly understood.
Acknowledgements
‘The authors acknowledge support from the Spanish CICYT (grant MAT92-388). MIDAS program and Universidad Complutense. 1 -
References
0
10
20
30
40
50
60
S.W. Tozer.
A.W.
F. Holtzberg. T2
(lo3
K2)
Fig. 2. Plot of cotangent of the Hall angle tJu at H = 9 T
the square of temperature for both
H.L.
versus
The inset shows RH in u-axis films (H ).
types ofqlm.
the reciprocal of the Hall cocfkient
Kleinsasser,
f.
Phys. Rev. Let t. 59
Stormer, A.F.J.
G.S. Boebinger,
Penney. D. Kaiser
Baldwin,
Levi. K.W.
and
(1987) i 768. M. Anzlowar
and
Phys. Rev. B 38 (1988] 2472.
L. Forro,
M. Raki. J.Y. Henry and C. Ayacne. Solid State
Commun.
69 (1989) 1097.
J.M. Harris. Y.F. ‘r’an and N.P. Ong. Phys. Rev. B 46 (1992j 14293. B. Wuyts.
E. Osquigcit.
M. Maenhoudt.
S. Libbrecht. Z.X.
temperature down to the transition. Also. the Hall resistivity p,, is positive in both kinds of film, although RH is
Ciao and Y. Bruynseraede. Phys. Rev. B 47 (1993) 5512. _fl . C.C. Jones, D.K. CI‘i-:-*IlSlCri. J.R. Thompson. R. Fccnstra:.
smaller in the mixed (I + c oriented samples. On the other hand. pure u-axis clriented films are metallic with an increasing slope of pxx( T) up to h 250 K. The Hall effect of our pure a-axis films is clearly negative, in agreement with the single crystal response [I, 33 but different from previous resu!?s [7]. The films of Lu et al. [7] show a clear (005) X-ray reflection (c-axis orientation) in the
S. Zhu. D.H.
Lowndes. J.M. Phillips,
M.P. Siegal and J.D.
Budai. Phgs. Rev. 847
( 1993) SO86
Y. Lu, B.R. Zha0.C.W.
Yuan, Y.Z. Zhang. Y.Y. Zhao. H.S.
Wang. Y.Y. 0. Nakamura.
Shi. P. Xu and L. Li. Z. Phys. B 74 (1959) 74. E.E. Fullerton.
J. Guimpei
and I.K. Schuller.
Appl. Phys. Lett. 60 (1992) 120. J. Colino.
J.L. Sacedbn and J.L. Viceni. Appt. Phys. Lett. 59
(1991) 3327.
Physica B 199&200 (1994) 246-247
Normal-state Hall effect in c-axis and a-axis oriented EuBa2Cu307 superconducting thin films J. Colino ~, J.l. Martiia b, J.L. Vicent b'* '~blstituto tte Ciem'ia tit, Materiales. C.S.L C. Serrano 144. MadrM 28006, Spai:~ Dcpartamento de Fisica de Materiales, Facuhad &, Fish'as. Unit,ersidad Comph~tense, Ciudad Universitaria s/n, MadrM 28040, Spain
Abstract Thin films of EuBa2Cu~O~ were obtained by DC magnetron sputtering on SrTiO3(1 0 0). The substrate temperature allows us to grow c-axis oriented ( ,-, 800 °C) or a-axis oriented ( ,.~ 680'~C) films. The DC four-sweep method was used to measure the Hall angle (0n) of patterned films between 100 and 250 K with applied magnetic fields up to 90 kOe. Samples with c-axis texture show ctg0H with the typical -,, T 2 behavior. In t 'rn, samples with a-axis orientation (H IIa-axis) show a negative Hall signal and ctg 0.d T) does not extrapolate to zero.
I. introduction
2. Experimental
The normal-state Hall effect of (RE)BaaCu~O7 superconducting cuprates has been extensively studied, for instance, as a function of temperature [1 4] and oxygen deficiency I-5,6]. In most of these works the magnetic field is perpendicular to the CuO2 planes (Hx), whereas the parallel field geometry (H 0 has scarcely been reported I1, 3]. The Hall coefficient (RH) is positive (holelike) in the Hi_ geometry, On the other hand, Rn is negative when both the current and magnetic field are parallel (H~) to the CuO2 planes. Thin films are very suitable for the Hall effect geometric requirements. However, the few reports of the Hti-Hail effect have been done in crystals. This fact arises from the usual c-axis orientation of the i :2:3 films. As far as we know there is only one previous report on the Hall coefficient of a-axis films [7_]. In this paper we report on the resistivity and Hall measurements of pure a-axis oriented and pure c-axis oriented thin films in the normal state.
Pure a-axis and pure c-axis oriented thin films have been grown by DC magnetron sputtering using the NACHOS technique I-8]. The details of sample preparation have been published elsewhere [9]. X-ray diffraction (Cu K,) shows the unique orientation (c- or a-axis perpendicular to the substrate) of our films on SrTiO3 (! 00),The patterned Hall bars exhibit narrow superconducting transition: ~ 2 K in c-axis films and ~ 4 K in a-axis films. A commercial 90 kOe supercond',zting solenoid, w~th H always lying perpendicular to the sut~strate, was used for the Hall measmements.
* Corresponding attthor.
3. Resuhs and discussion Figure 1 and the inset show the Hall resistivity and longitudinal resistivity, respectively, for pure a-axis films, pure c-axis films and mixed oriented a + c films. It can be seen that the resistivity P.,x of pucc c-axis and mixed a + c oriented films I "-- 5% c-orientation) is linear in
(P~21-4526 94.$07.00 ~) 1994 Elsevier Science B.V. All rights reserved S~DI 0921-4526(93)E0215-3
1. Cohn
0
100200300
c*-
T(K)
9 -=
-
1
QX
dC o _,&L/;.“.“‘” 1L.
cc
ce
cl al. / PIysica
/=
cc
40
-
... ..f,,...,...... ..,. _,__.... ..“” ,.._.._....
----_ _._
---__
---.____
.
-1 2
0
4
6
8
1c
H(T) Fig. I. Hall resistivity
versus magnetic field at -
100 K for pure
c-axis films (dashed line), pure a-axis films (solid line) and mixed a + c
films (dotted
temperature
line). The inset shows the resistivity
versus
of the same films.
B I99&200
( 19941
?4b -247
247
Bragg scans. Since we measure a-axis films with no trace of (001) reflections, the negative RH is an intrinsic property of 1: 2: 3 films in H,, geometry. From the Hall coefficient at + 100 K we can estimate, in a free electron model, a number of carriers per unit cell of the order of 1.6 ( - ) in cl-axis films and 0.5 ( + ) in c-axis films. These values are very close to those of single crystals [ 1,3]. The rtg& ( = pxx/p,) of c-axis films (Fig. 2) shows a - T2 behavior, similar to that previously reported [l-6]. a-axis oriented films have a rather insensitive temperature dependence of l/R” (see the inset of Fig. 2). The fact that these experiments have been done in patterned thin films rules out a possible influence of sample shape in the Hall measurement. The ctg& of a-axis films does not extrapolate to zero at low temperatures, rather it slightly changes with temperature. In summary, we have measured the Hall angle of pure c-axis oriented films, pure a-axis oriented films and mixed a + c oriented films. In pure a-axis films R,,(HI(a) - - 6101-‘~ m”/C agrees with previous single crystal data [ 1,3]. We have also shown that small amounts of c-axis orientation drastically change the If,,Hall coefficient, even turning to hole-like conduction. In contrast to the behavior of the Hall angle in c-axis films. both RH and ctg Onof a-axis films are rather insensitive to temperature. This point is not yet clearly understood.
Acknowledgements
‘The authors acknowledge support from the Spanish CICYT (grant MAT92-388). MIDAS program and Universidad Complutense. 1 -
References
0
10
20
30
40
50
60
S.W. Tozer.
A.W.
F. Holtzberg. T2
(lo3
K2)
Fig. 2. Plot of cotangent of the Hall angle tJu at H = 9 T
the square of temperature for both
H.L.
versus
The inset shows RH in u-axis films (H ).
types ofqlm.
the reciprocal of the Hall cocfkient
Kleinsasser,
f.
Phys. Rev. Let t. 59
Stormer, A.F.J.
G.S. Boebinger,
Penney. D. Kaiser
Baldwin,
Levi. K.W.
and
(1987) i 768. M. Anzlowar
and
Phys. Rev. B 38 (1988] 2472.
L. Forro,
M. Raki. J.Y. Henry and C. Ayacne. Solid State
Commun.
69 (1989) 1097.
J.M. Harris. Y.F. ‘r’an and N.P. Ong. Phys. Rev. B 46 (1992j 14293. B. Wuyts.
E. Osquigcit.
M. Maenhoudt.
S. Libbrecht. Z.X.
temperature down to the transition. Also. the Hall resistivity p,, is positive in both kinds of film, although RH is
Ciao and Y. Bruynseraede. Phys. Rev. B 47 (1993) 5512. _fl . C.C. Jones, D.K. CI‘i-:-*IlSlCri. J.R. Thompson. R. Fccnstra:.
smaller in the mixed (I + c oriented samples. On the other hand. pure u-axis clriented films are metallic with an increasing slope of pxx( T) up to h 250 K. The Hall effect of our pure a-axis films is clearly negative, in agreement with the single crystal response [I, 33 but different from previous resu!?s [7]. The films of Lu et al. [7] show a clear (005) X-ray reflection (c-axis orientation) in the
S. Zhu. D.H.
Lowndes. J.M. Phillips,
M.P. Siegal and J.D.
Budai. Phgs. Rev. 847
( 1993) SO86
Y. Lu, B.R. Zha0.C.W.
Yuan, Y.Z. Zhang. Y.Y. Zhao. H.S.
Wang. Y.Y. 0. Nakamura.
Shi. P. Xu and L. Li. Z. Phys. B 74 (1959) 74. E.E. Fullerton.
J. Guimpei
and I.K. Schuller.
Appl. Phys. Lett. 60 (1992) 120. J. Colino.
J.L. Sacedbn and J.L. Viceni. Appt. Phys. Lett. 59
(1991) 3327.