Magnetic coupling between Gd and Pr ions and magnetocaloric effect in Gd 0.5 Pr

ARTICLE IN PRESS

  Journal of Magnetism and Magnetic Materials 321 (2009) 3014–3018

  Contents lists available at

  

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  journal homepage:

  Magnetic coupling between Gd and Pr ions and magnetocaloric effect in Gd Pr Al compound

  0.5

  0.5

  2

  a, b c c d e

A. Magnus G. Carvalho , F. Garcia , V.S.R. de Sousa , P.J. von Ranke , D.L. Rocco , G.D. Loula ,

  b e f e E.J. de Carvalho , A.A. Coelho , L.M. da Silva , F.C.G. Gandra a

-

b

Divisa ˜o de Metrologia de Materiais (DIMAT), Instituto Nacional de Metrologia, Normalizac a ˜o e Qualidade Industrial (INMETRO), Duque de Caxias, Rio de Janeiro, 25250-020, Brazil

c Laborato ´rio Nacional de Luz Sı´ncrotron (LNLS), Campinas, Sa ˜o Paulo, Brazil d Instituto de Fı´sica, Universidade do Estado do Rio de Janeiro-UERJ, Rua Sa ˜o Francisco Xavier, 524, 20550-013, Rio de Janeiro, Brazil e Departamento de Fı´sica, Universidade Federal de Ouro Preto, 35400-000, Ouro Preto, MG, Brazil f Instituto de Fı´sica ‘‘Gleb Wataghin’’, Universidade Estadual de Campinas, Unicamp, 13083-970, Campinas, Sa ˜o Paulo, Brazil

  Centro de Cieˆncias Sociais, Sau ´de e Tecnologia (CCSST), Universidade Federal do Maranha ˜o, Imperatriz-MA, Brazil a r t i c l e i n f o a b s t r a c t

Article history: In this work, we report the theoretical and experimental investigations on the magnetic and

Received 18 March 2009 magnetocaloric properties for Gd Pr Al compound in different magnetic fields. The magnetization

  0.5

  0.5

  2 Available online 7 May 2009

  features indicate that Gd Pr Al is ferrimagnetic at low temperatures. We also present data from

  

0.5

  0.5

  2 X-ray magnetic circular dichroism (XMCD) experiments for this compound, with which we have PACS:

  confirmed that the magnetic moments of the Pr ions are antiparallel to the magnetic moments of the Gd

  71.20.Eh

  74.25.Ha

  ions. The magnetocaloric parameters, DT and DS , were obtained from calorimetric data and both

  S T

  87.64.Ni

  curves present normal and inverse magnetocaloric effect. A theoretical model for ferrimagnetic coupling, including the crystalline electrical field anisotropy, was used to describe the DT and DS

  S T Keywords: experimental results.

  Rare-earth alloy

  & 2009 Elsevier B.V. All rights reserved.

  X-ray magnetic circular dichroism Ferrimagnetism Magnetocaloric effect

  1. Introduction field-induced transitions or even high crystal field anisotropy.

  For this reason, it is our goal to investigate the role of rare-earth microscopic interactions into the magnetic properties of the RAl (R ¼ rare-earth) compounds with cubic Laves phase have

  2 compounds and consequently its magnetocaloric behavior.

  been extensively studied and the ground state is found to be In this paper, we discuss our results on X-ray magnetic circular ferromagnetic for most of them. GdAl is ferromagnetic with a

  2

  dichroism (XMCD), magnetization and magnetocaloric effect Curie temperature laying between 153 and 182 K and its effective

  (MCE) for the Gd Pr Al compound. Using the XMCD technique, magnetic moment is around 7.93 B . The Curie temperature

  0.5

  0.5

  2 m

  we intend to investigate the antiparallel coupling between Pr of the PrAl compound is around 34 K and its effective magnetic

  2

  and Gd atoms, as it has been proposed in the literature to be moment is 3.5 B These distinct characteristics can induce

  m

  antiparallel . The MCE data for the compounds GdAl and PrAl interesting ground states for a system where the two rare-earth

  2

  2

  have been reported elsewhere and in the present work we compounds, Gd and Pr, occupy the R site in the RAl

  2 cubic lattice.

  report on the MCE for Gd Pr Al . Our experimental results will In fact, Williams et al. have studied five systems R R Al ,

  0.5

  0.5

  2 1 x x

  2

  be compared to calculations obtained using a theoretical model where R and R ¼ rare-earth elements, including the series that takes in account the coupling between the two magnetic

  Gd Pr Al . Their experimental work has indicated that the

  1 x x

  2 sublattices.

  systems in which both lanthanides are light (the ions occurring before Eu) or alternatively both are heavy (the ions from Gd to Lu) couple ferromagnetically, whereas for light–heavy combinations the coupling is ferrimagnetic. Such compounds are interesting in

  2. Experimental procedure terms of the magnetocaloric effect (MCE), because they can present Polycrystalline samples of Gd Pr Al , GdAl and PrAl

  0.5

  0.5

  2

  2

  2

  compounds were prepared by arc-melting the elements in high- purity argon atmosphere on a water-cooled copper hearth. The

  Corresponding author.

  purity of the starting materials was 99.99 wt% for aluminum and E-mail address:

  0304-8853/$ - see front matter & 2009 Elsevier B.V. All rights reserved.

ARTICLE IN PRESS

  Þ þ 12R

  P b d i d i

  e

  b d i

  þ k

  B

  ln X d i e

  @ b d i 1 A

  , (10) The lattice contribution to the entropy is obtained using the

  Debye formula S

  d lat

  ðTÞ ¼ 3R lnð1 e

  y d D =T

  y d D

  d i

  T !

  3 Z y d D =T

  x

  3

  dx e

  x

  1 ;

  (11) where R is the gas constant and y D the Debye temperature. The electronic contribution to the total entropy is calculated by means of usual expression:

  S

  el

  ðTÞ ¼ ¯ g

  d

  e

  1 T P d i

  g was taken as 9.87 mJ mol

  the angles formed by the applied magnetic field with the Cartesian axes. Then, the total magnetiza- tion for Gd

  cos b þ M

  d z

  cos

  g

  , (8) where M

  d k

  (k ¼ x, y, z) are the Cartesian components of the magnetization and

  a

  ,

  b

  and

  g

  0.5 Pr

  ðT ; BÞ ¼

  0.5 Al

  2

  is: M

  B

  ðT ; BÞ ¼ 0:5M

  Gd B

  ðT ; BÞ þ 0:5M

  Pr B

  ðT ; BÞ,

  (9) The magnetic entropy can be calculated from the general relation

  S

  d mag

  T, (12) where the Sommerfeld coefficient ¯

  1 K

  þ M

  D S T

  l Pr

  ¼ 0.21 meV/

  m B

  , obtained by comparing the calculated critical temperature with the experimental one. The CEF parameters, x ¼ 0.739 and W ¼ 0.329 meV, were taken from Ref. for PrAl

  2 . The applied field was

  chosen to be in the [10 0] direction (the easy direction of magnetization of PrAl

  2 ).

  The magnetocaloric thermodynamic quantities, D S

  T

  and D T

  S

  , are calculated by means of the usual relations:

  ðT ; BÞ ¼ S

  m B

  tot

  ðT ; B ¼ 0Þ S

  tot

  ðT ; Ba0Þ, (15)

  D T S

  ðT ; BÞ ¼ TðT; Ba0Þ TðT; B ¼ 0Þ, (16)

  4. Results and discussion The magnetic transition temperature of Gd

  0.5 Pr

  0.5 Al

  2

  compound is around 108 K, obtained from derivatives of the magnetization curves shown in and it has an effective magnetic moment of 5.4 m B . After reducing temperature of the system in zero magnetic field (ZFC process), the thermomagnetic curves were measured on

  A.M.G. Carvalho et al. / Journal of Magnetism and Magnetic Materials 321 (2009) 3014–3018 3015

  and

  ¼ 0.49 meV/

  2

  0.5 Al

  , which is an average of the values of ¯ g for the compounds LaAl

  2 and LuAl 2 .

  The entropy of each magnetic sublattice is considered as the summation of the three main contributions described above: S

  d

  ðT ; BÞ ¼ S

  d mag

  ðT ; BÞ þ S

  d lat

  ðTÞ þ S

  d el

  ðTÞ, (13) and for the compound Gd

  0.5 Pr

  2

  l Gd Pr

  we have: S

  tot

  ðT ; BÞ ¼ 0:5S

  Gd

  ðT ; BÞ þ 0:5S

  Pr

  ðT ; BÞ,

  (14) To calculate the magnetocaloric effect, we adopted the values:

  l Gd

  ¼ 1.70 meV/

  m B

  ,

  d y

  99.9 wt% for the rare-earth metals. We have repeated the melting were subsequently annealed under argon atmosphere in a quartz ampoule at 1270 K for 5 h. The X-ray diffraction analyses for all samples show a single-phase formation with the C15 cubic Laves phase structure.

  The XMCD measurements were performed on the dispersive

  21O

  CF

  ¼ W x F

  4

  ðO

  4

  þ 5O

  4

  4

  Þ þ 1 jxj F

  6

  ðO

  6

  4

  Pr m

  6

  Þ (4)

  In relation (4), O

  m n

  are the Stevens equivalent operators and W and x the parameters that determine, respectively, the strength and the ordination of the splitting of the (2J+1)-fold degenerate Hund ground state, F

  4 and F 6 are dimensionless constants

  The molecular fields ~ B

  Gd m

  and ~ B

  Pr m

  (which couple the Gd and Pr sublattices) can be written as follows: ~

  B

  the molecular field acting on Gd and Pr ions, respectively, and~ J the total angular momentum operator. Besides the molecular and applied magnetic fields, the 4f electrons of the Pr ions experience the influence of a crystalline electrical field (CEF), which for cubic symmetry (in the Lea– Leask–Wolf notation) is given by H

  and ~ B

  ¼

  Gd m

  XAS beam line at the Brazilian Synchrotron Light Laboratory (LNLS, Campinas, Brazil). A right circularly polarized X-ray beam was selected by a 0.1 mm-wide slit, positioned at half intensity above the orbit plane (maximum intensity), ensuring a circular polarization rate from approximately 0.7. Data were recorded in transmission mode, fixing the polarization and reversing the 0.9 T permanent magnetic field, applied along the beam propagation direction.

  The magnetic measurements were performed in a commercial SQUID magnetometer (Quantum Design) and the calorimetric experiments were performed in the commercial equipment (PPMS; Quantum Design).

  3. Theoretical description To calculate the magnetic and magnetocaloric properties of the

  Gd

  0.5 Pr

  0.5 Al

  2

  compound, we consider a two-magnetic-sublattice Hamiltonian: H ¼ HðGdÞ þ HðPrÞ,

  (1) where: HðGdÞ ¼ g

  Gd m

  B

  ½~ B þ ~ B

  :~ J

  Gd m

  Gd

  , (2) HðPrÞ ¼ g

  Pr m

  B

  ½~ B þ ~ B

  Pr m

  :~ J

  Pr

  þ H

  CF

  , (3) Relations (2) and (3) are the single-ion Hamiltonian of Gd and

  Pr coupled sublattices, g the Lande´ factor, m B the Bohr magneton, ~ B the applied magnetic field, ~ B

  Gd m

  l Gd

  cos

  j

  i ¼ g

  d m

  B

  h~ J

  d

  i ¼ g

  d m

  B P d i

  h

  d i

  j~ J

  d

  d i

  ¼ h~

  ie

  P b d i d i

  e

  b d i

  , (7) where b ¼ 1/k

  B

  T and k

  B is the Boltzmann constant.

  The projection of the magnetization of Gd and Pr ions along the applied magnetic field direction is given by M

  d B

  ðT ; BÞ ¼ M

  d x

  m d

  d

  ~ M

  þ

  Gd

  þ

  l Gd Pr

  ~ M

  Pr

  (5) and ~

  B

  Pr m

  ¼

  l Pr

  ~ M

  Pr

  l Gd Pr

  M

  ~ M

  Gd

  (6) where l Gd , l Gd–Pr and l Pr are, respectively, the molecular field parameters for Gd ions, Gd–Pr ions and Pr ions interactions, and

  ~ M

  Gd

  and ~ M

  Pr are the magnetization of each ion sublattice.

  From the eigenvalues

  d k

  and eigenvectors |

  d k

  S ( d ¼ Gd, Pr) obtained from the usual relation: ~

  a

ARTICLE IN PRESS

  3016 A.M.G. Carvalho et al. / Journal of Magnetism and Magnetic Materials 321 (2009) 3014–3018

35 Gd Pr AI

  B = 0.02 T

  30

  25 )

  • 1
  • 1

  .kg

  2

  15K

  20

  50K

  • 2

  70K

  15

  90K

  XMCD (%)

  10 100K

  Magnetization (A.m

  • 3 115K

  5

  • 4

  Gd Pr AI

  0.5

  0.5

  2

  20

  40

  60 80 100 120 Temperature (K) Energy (a.u.) Fig. 1. Magnetization as a function of temperature, in a magnetic field of 0.02 T.

  The heating and cooling curves were measured after a zero-field-cooling process.

  Fig. 3. X-ray magnetic circular dichroism obtained in several temperatures at Gd L III edge for the Gd 0.5 Pr 0.5 Al 2 compound. The inset shows XMCD signal for the GdAl 2 compound at the same edge.

  80

  1 T

  2 T

  70

  3 T

  5

  60

  4 T )

  Gd Pr AI

  0.4

  0.5

  0.5

  2

  • 1

  5 T .kg

  2

  50

  0.0

  4

  40

  • 0.4

  15 K

  25 K Pr L edge II

  30

  3

  • 0.8

  XMDC (%)

  70 K PrAI 2

  18 K Magnetization (A.m

  20

  • 1.2

  90 K

  2

10 Energy (a.u.)

  XMDC (%)

  1

  20

  40

  60 80 100 120 140 Temperature (K)

  Fig. 2. Magnetization as a function of temperature, in different magnetic fields, for the Gd 0.5 Pr 0.5 Al 2 compound.

  field. We observe that in the heating process the magnetization is

  • 1

  lower when compared to the cooling cycle, but both curves show a maximum just below the transition temperature. These features

  Energy (a.u.)

  (minima and maxima) are consistent with a ferrimagnetic coupling

  Fig. 4. X-ray magnetic circular dichroism obtained in several temperatures at Pr L II . edge for the Gd 0.5 Pr 0.5 Al 2 compound. The inset shows XMCD signal for the PrAl 2 In we show the field-cooled magnetization as a function compound at the same edge.

  of the temperature measured at different magnetic fields. In the inset of this figure one can see a minimum followed by a maximum as the temperature increases. We believe that the the XMCD profiles at several temperatures obtained from the minimum observed can be due to the Pr magnetic sublattice absorption data at Gd L edge. We notice that the XMCD signal is

  III

  (antiparallel to the Gd sublattice), which could be composed consistently reduced with increasing temperature and fades out by non-collinear magnetic moments that tend to align while above 108 K, the transition temperature. The inset in shows temperature is increased until achieving the temperature the XMCD signal for GdAl 2 , used as a reference compound. of the minimum. However, this hypothesis must be checked by Since both Gd Pr Al and GdAl present negative signals, we

  0.5

  0.5

  2

  2

  some technique, such as, X-ray magnetic diffraction on a single can conclude that the Gd moments are oriented parallel to the crystal of the Gd Pr Al compound. The maximum in the external magnetic field in both materials.

  0.5

  0.5

  2

  thermomagnetic curves can be originated by different behaviors On the other hand, X-ray absorption measurements at Pr L

  II

  between Pr and Gd magnetic sublattices as a function of the edge at different temperatures resulted in the XMCD profiles for temperature.

  Gd

  0.5 Pr

  0.5 Al 2 shown in . By comparing with the Gd results,

  We present in the results on X-ray magnetic we see that the Pr L signal is inverted. To know if magnetic

  II

ARTICLE IN PRESS

0.5 Pr

1 K

  4

  3

  • 1
  • 1

  ¼ 2.16 and

  0.5 Pr

  1.0

  1.5

  2.0

  1

  2

  Thus, we have performed calculations considering g

  Gd eff

  present a transition at 108 K, in an intermediary position. Magnetization data indicates that the compound does not show a ferromagnetic behavior, in agreement

  2

  0.5 Al

  ferromagnetic, while Gd

  m Gd teo

  2 (T C between 153 and 182 K) and PrAl 2 (T C ¼ 34 K) are

  The base compounds, GdAl

  0.5

  0.5 Pr

  5. Conclusions In this work, we studied the thermomagnetic properties of the pseudo-binary compound Gd

  ¼ 2 and W ¼ 0.879 meV. The theoretical magnetization reproduces well the experimental data and it is an indication that the CEF influence could be responsible for the large magnetization at low temperatures, as well as the larger Gd magnetic moments (5d electrons contribution).

  Gd eff

  Besides that, we may suppose that the divergence between experimental and theoretical (set 1) magnetization at 5 T and low temperatures could be also an indicative of the non-collinear magnetic moments in the Pr sublattice. Supposing that the non- collinear behavior could be a manifestation of a modified crystal- line field acting on the Pr magnetic sublattice, we used other set of parameters (set 3), which considers g

  (set 2) and, at low temperatures, the theoretical magnetization isofield is closer to the experimental data, when compared to results from set 1 (

  m B

  ¼ 7.55

  0.5 Al 2.

  20

  0.0

  3.0

  Fig. 6. Experimental (symbol) and theoretical (solid, dashed and dotted lines) magnetization isofields for Gd 0.5 Pr 0.5 Al 2 compound measured at 5 T. Set 1 (g Gd eff ¼ 2); set 2 (g Gd eff ¼ 2.16); set 3 (g Gd eff ¼ 2, W ¼ 0.879). A.M.G. Carvalho et al. / Journal of Magnetism and Magnetic Materials 321 (2009) 3014–3018 3017

  /f.u.) Experimental Theory (set 1) Theory (set 2) Theory (set 3)

  M ( µ B

  60 80 100 120 140 Temperature (K) B = 5T

  40

  20

  0.0

  0.5

  1.0

  1.5

  2.0

  2.5

  T S ) as a function of the temperature for Gd 0.5 Pr 0.5 Al 2 compound. Both were obtained for a magnetic Gd Gd Gd

  40

  D

  S T ) as a function of the temperature and (b) adiabatic variation of the temperature (

  D

  ) Fig. 5. Experimental (symbols) and theoretical (solid, dashed and dotted lines) results for (a) isothermal variation of the entropy (

  .K

  T (J.kg

  Experimental Theory (set 1) Theory (set 2) Theory (set 3)

  S (K)

  2 Δ T

  0.5 AI

  0.5 Pr

  60 80 100 120 140 160 180 Temperature (K) Gd

  0.5 Al 2 compound.

  between theoretical and experimental magnetization at 5 T and low temperatures could be an indicative of the influence of the 5d electron in the total magnetic moment of Gd

  0.5 Pr

  temperature, the XMCD signal decreases, following the same behavior observed in the measurements at Gd L

  S

  D

  and 1.7 K, respectively. We notice that there is an inverse magnetocaloric effect (both

  1

  2 T. D S T and D T S are the thermodynamic quantities defined in relations (15) and (16) that characterize the magnetocaloric effect. For the magnetic field variation from 0 to 2 T, the maximum values of D S T and D T S are 4.1 J kg

  compound obtained from specific heat data collected at 0 T and

  2

  0.5 Al

  0.5 Pr

  ) and the adiabatic variation of the temperature ( D T S ) for Gd

   shows the isothermal variation of the entropy ( D S T

  III edge.

  0.5 Al 2 compound. By increasing the

  and

  these moments are antiparallel to the magnetic field. This definitely shows that the magnetic moments of the Pr ions are antiparallel to the magnetic moments of the Gd ions in the Gd

  2

  0.5 Al

  0.5 Pr

  conclude that in Gd

  2 compound are parallel to the applied magnetic field, we

  compound. Since the magnetic moments of the Pr ions in the PrAl

  2

  0.5 Al

  0.5 Pr

  negative and contrary to the one observed in the Gd

  2 compound. We note that this signal is

  magnetic field, it is necessary to compare with a ferromagnetic the ferromagnetic PrAl

  T

  D

  m B The difference of almost 0.3 m B

  T and D T S results.

  ffi7.55

  m exp Gd

  for Gd magnetic moment, while experimental results for pure Gd show that

  m B

  ¼ 7.0

  m Gd teo

  (symbols). The theoretical model (set 1) considers

  m B

  0 K (dotted line in the ), while experimental magnetization at T ¼ 2 K and at the same magnetic field is around 2.21

  m B at 5 T and near

  ¼ 7.0) yields a magnetization of 1.93

  m Gd teo

  Supposing collinear magnetic moments, the theoretical model (set 1,

  S

  T

  D

  ¼ 2 and W ¼ 0.879 meV. In spite of the differences among the theoretical curves, it is hard to guess which is the best physical scheme for only analyzing

  Gd eff

  ¼ 2.16; the set 3 considers g

  Gd eff

  ¼ 2 and the other parameters described in the theory section; the set 2 considers g

  Gd eff

  curves that also present the inverse magnetocaloric effect. The set 1 includes g

  S

  and D T

  T

  present negative values) at low temperatures. This is certainly due to the ferrimagnetic coupling between Pr and Gd ions. Using different sets of parameters in the theoretical model described above, we obtain D S

  S

  • Δ S
  • 1
  • 0.5

ARTICLE IN PRESS

  3018 A.M.G. Carvalho et al. / Journal of Magnetism and Magnetic Materials 321 (2009) 3014–3018

  confirmed that the magnetic moments of the Pr ions are oriented References the magnetization suggests that the minima that occur in the [1] K.H. Mader, E. Segal, W.E. Wallace, J. Phys. Chem. Solids 30 (1969) 1.

  [2] S. Bakanowski, J.E. Crow, N.F. Berk, T. Mihalisin, Solid State Commun. 17 (1975)

  thermomagnetic curves are due to non-collinear magnetic mo- 1111. ments in the Pr sublattice. Both experimental and theoretical

  [3] P. Miles, M.A.A. Issa, K.N.R. Taylor, G.J. Bowden, J. Phys. F: Metal Phys. 7 (11) D S T and D T S results present inverse MCE at low temperatures, (1977) 2421.

  [4] B. Barbara, M.F. Rossignol, M. Uehara, Physica B 86–88 (1977) 183.

  which is expected for a ferrimagnetic material. The comparison [5] E. du Tremolet de Lacheisserie, J. Magn. Magn. Mat. 73 (1988) 289. between calculations and experimental magnetization isofield [6] N. Nereson, C. Olsen, G. Arnold, J. Appl. Phys. 19 (10) (1968) 4605. curves suggests that the CEF acting on Pr ions and the 5d electrons

  [7] H.J. Williams, J.H. Wernick, R.C. Sherwood, E.A. Nesbitt, J. Phys. Soc. Jpn 17 (Suppl. B-I) (1961) 91.

  from Gd ions could be contributing to the magnetization of [8] K.A. Gschneidner Jr., V.K. Pecharsky, M.J. Gailloux, H. Takeya, Adv. Cryog. Eng. Gd Pr Al compound.

  0.5

  0.5

  2 42 (1996) 465.

  [9] A. Magnus G. Carvalho, J.C.P. Campoy, A.A. Coelho, E.J.R. Plaza, S. Gama, P.J. von Ranke, J. Appl. Phys. 97 (2005) 083905. [10] K.R. Lea, M.J.M. Leask, W. Wolf, J. Phys. Chem. Solids 23 (1962) 1382–1485. [11] K.W.H. Stevens, Proc. Phys. Soc. Sect. A 65 (1952) 209–215.

  Acknowledgements

  [12] P.J. von Ranke, V.K. Pecharsky, K.A. Gschneidner Jr., Phys. Rev. B 58 (1998) 12110.

  The authors acknowledge the financial support from the [13] H.G. Purwins, A. Leson, Adv. Phys. 39 (1990) 309–403.

  [14] W.M. Swift, W.E. Wallace, J. Phys. Chem. Solids 29 (1968) 2053.

  Brazilian agencies CAPES, FAPESP, FAPERJ and CNPq. The authors [15] L. Ne´ll, Ann. Phys. 3 (1948) 137. are also grateful to Laborato´rio Nacional de Luz Sı´ncrotron (LNLS)

  [16] D.R. Lide, Handbook of Physics and Chemistry, eighty-fifth ed., CRC Press, Boca and Francisco Paulo Rouxinol for the discussions.

  Raton, FL, 2004.

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REPOSITORIO INSTITUCIONAL DA UFOP: Modeling mono- and multi-component adsorption of cobalt(II), copper(II), and nickel(II) metal ions from aqueous solution onto a new carboxylated sugarcane bagasse. Part I: Batch adsorption study.

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MAGNETOMETRIC AND GAMMA SPECTROMETRIC EXPRESSION OF SOUTHWESTERN S˜AO FRANCISCO BASIN, SERRA SELADA QUADRANGLE (1:100.000), MINAS GERAIS STATE Humberto Luis Siqueira Reis 1,2,3 , Maria S´ılvia Carvalho Barbosa1, Fernando Flecha de Alkmim1 and Antonio Carl

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Magnetic scavenging of ultrafine hematite from itabirites Concentração magnética esgotadora de ultrafinos itabiríticos

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E. Yokoyama - REPOSITORIO INSTITUCIONAL DA UFOP: Magnetic fabric of Araguainha complex impact structure (Central Brazil) : implications for deformation mechanisms and central uplift formation.

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