BRAZILIAN CENTER FOR RESEARCH IN PHYSICS CBPF MCT

BRAZILIAN CENTER FOR RESEARCH IN PHYSICS- CBPF / MCT www. cbpf. br HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

CBPF - National Institute/MCT Rio de Janeiro www. cbpf. br Jacques Danon HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Magnetic and Structural Transitions in the New Fe-pnictide Superconductors Elisa Baggio Saitovitch Julian Munevar, CBPF Mariella Alzamora, CBPF Dalber Sanchez-Candela, UFF HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Collaborators Samples grown - Physical characterization Hai Hu Wen IOP, National Superconductivity Laboratory, China G. F. Cheng and N. L. Wang Institute of Physics, Chinese Academy of Sciences, Beijing, Peoples Republic of China S. L. Budko and P. C. Canfield Ames Laboratory, U. S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, USA Tomo Uemura Columbia University , NY, USA Graeme Luke Mc. Master University, ON, Canada CIAM Collaboration Program (NSF/CNPq) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Hideo Hosono started with Iron-Based Layered SC: La. OFe. P (Tc=6 K) to Sm. Fe. As. O 1 -x (Tc= 55 K) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Iron-based layered compound Ln. OFe. As “ 1111 phase” The discovery of superconductivity in fluorine doped La. Fe. As. O superconductor with TC = 26 K* has generated enormous interests in the community of superconductivity F-substitution La. Fe. As. O 1 -x. Fx O-deficiency Ln. Fe. As. O 1 -y Tc=55 K in Sm. Fe. As. O 1−δ *Y. Kamihara, et al, J. Am. Chem. Soc. 130, 3296 (2008). La. OFe. As -> (Tc = 26 K) SC under • doping with F– • oxygen deficiency Z. A. Ren et al. Europhys. Lett. 83 17002 (2008) Ln substitution (Gd 3+ Th 4+) Tc up to 56 K for (Gd, Th)Fe. As. O Cao Wang et al EPL 83 67006 (2008) **Hiroki Takahashi, Nature 453, 376 (2008) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Iron-arsenide- 1111 and 122 Phases Fe As Fe has tetrahedral coordination and is formally divalent 1111 ROFe. As R=La, ……. . , Gd 122 AFe 2 As 2 A=Ba, Ca Sr, Eu The crystal is composed of a stack of alternating REO or A and Fe. As layers. *D. Johrendt and R. Pottgen, Angew. Chem. Int. Ed. 47, 4782 (2008). HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

In 2008 More than 700 papers Increase of T C of RE(O, F)Fe. As superconductor after announcement by Hosono on Feb. , 2008, made by Chinese physicists including PI Wang and LE Wen HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Catalogue of Fe-based Superconductors Fe-1111 Ln. Fe. PO Tc~5 -6 K ( Tc~8. 8 K at Pressure ~0. 8 GPa) Ln. Fe. As. O 1 -x. Fx La. Fe. As. O 1 -x. Fx x=0. 11, Tc~26 K (Tc~43 K at P~4 GPa) Ce. Fe. As. O 1 -x. Fx x=0. 16, Tc~41 K Sm. Fe. As. O 1 -x. Fx x=0. 10, Tc~43 K Nd. Fe. As. O 1 -x. Fx x=0. 11, Tc~52 K Pr. Fe. As. O 1 -x. Fx x=0. 11, Tc~52 K Tb. Fe. As. O 1 -x. Fx Tc~46 K (x=0. 1, 0. 2) Dy. Fe. As. O 1 -x. Fx Tc~45 K (x=0. 1, 0. 2) Ln. Fe. As. O 1 -x La. Fe. As. O 1 -x 31. 2 Ce. Fe. As. O 1 -x 46. 5 Pr. Fe. As. O 1 -x 51. 3 Nd. Fe. As. O 1 -x 53. 5 Sm. Fe. As. O 1 -x 55. 0 Gd. Fe. As. O 1 -x 53 e Tb. Fe. As. O 1 -x 52 Dy. Fe. As. O 1 -x 52 (Ln, RE)Fe. As (La 1 -x. Srx)Fe. As. O Tc~ 25 K(x=0. 13), hole-doping Gd 1 -x. Thx)Fe. As. O Tc~56 K (x=0. 2), electron-doping Ca(Sr)Fe. As. F Ca(Fe 1 -x. Cox)As. F Tc~22 K (x=0. 10) [Ni 2+(3 d 7) Fe 2+(3 d 6)] Ca(Fe 1 -x. Nix)As. F Tc~12 K (x=0. 05) [Ni 2+(3 d 8) Fe 2+(3 d 6)] (Sr 1 -x. Lax)Fe. As. F Tc~32 K (x=0. 4) Fe-122 Ca. Fe 2 As 2 Tc~27 K (Pressure~3. 0 GPa) (Ba 1 -x. Kx)Fe 2 As 2 Tc~38 K (x=0. 4) (Sr 1 -x. Nax)Fe 2 As 2 Tc~37 K (x=0. 4) Ba(Fe 1 -x. Cox)2 As 2 Tc~22 K (x=0. 1) Fe -111 Li 1 -x. Fe. As Tc~18 K Fe-42622 Sc 42622 V 42622 Fe-11 Fe. Se 1 -x Tc~8 K (x=0. 88), Tc~27 K (P~ 1. 48 GPa) Fe. Se 1 -x. Tex Tc~15 K Fe. Te 1 -x. Sx Tc~10 K (x=0. 2), non-toxic RFe. As. O 1 -x. Fx , AFe 2 As 2, Fe-1111 Fe- 122 Sr 4 A 2 O 6 Fe 2 As 2 Fe - 42622 HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Catalogue of Fe-based Superconductors Fe-1111 Ln. Fe. PO Tc~5 -6 K ( Tc~8. 8 K at Pressure ~0. 8 GPa) Ln. Fe. As. O 1 -x. Fx La. Fe. As. O 1 -x. Fx x=0. 11, Tc~26 K (Tc~43 K at P~4 GPa) Ce. Fe. As. O 1 -x. Fx x=0. 16, Tc~41 K Sm. Fe. As. O 1 -x. Fx x=0. 10, Tc~43 K Nd. Fe. As. O 1 -x. Fx x=0. 11, Tc~52 K Pr. Fe. As. O 1 -x. Fx x=0. 11, Tc~52 K Tb. Fe. As. O 1 -x. Fx Tc~46 K (x=0. 1, 0. 2) Dy. Fe. As. O 1 -x. Fx Tc~45 K (x=0. 1, 0. 2) Ln. Fe. As. O 1 -x La. Fe. As. O 1 -x 31. 2 Ce. Fe. As. O 1 -x 46. 5 Pr. Fe. As. O 1 -x 51. 3 Nd. Fe. As. O 1 -x 53. 5 Sm. Fe. As. O 1 -x 55. 0 Gd. Fe. As. O 1 -x 53 e Tb. Fe. As. O 1 -x 52 Dy. Fe. As. O 1 -x 52 (Ln, RE)Fe. As (La 1 -x. Srx)Fe. As. O Tc~ 25 K(x=0. 13), hole-doping Gd 1 -x. Thx)Fe. As. O Tc~56 K (x=0. 2), electron-doping Ca(Sr)Fe. As. F Ca(Fe 1 -x. Cox)As. F Tc~22 K (x=0. 10) [Ni 2+(3 d 7) Fe 2+(3 d 6)] Ca(Fe 1 -x. Nix)As. F Tc~12 K (x=0. 05) [Ni 2+(3 d 8) Fe 2+(3 d 6)] (Sr 1 -x. Lax)Fe. As. F Tc~32 K (x=0. 4) Fe-122 Ca. Fe 2 As 2 Tc~27 K (Pressure~3. 0 GPa) (Ba 1 -x. Kx)Fe 2 As 2 Tc~38 K (x=0. 4) (Sr 1 -x. Nax)Fe 2 As 2 Tc~37 K (x=0. 4) Ba(Fe 1 -x. Cox)2 As 2 Tc~22 K (x=0. 1) Fe -111 Li 1 -x. Fe. As Tc~18 K Fe-42622 Sc 42622 V 42622 Fe-11 Fe. Se 1 -x Tc~8 K (x=0. 88), Tc~27 K (P~ 1. 48 GPa) Fe. Se 1 -x. Tex Tc~15 K Fe. Te 1 -x. Sx Tc~10 K (x=0. 2), non-toxic RFe. As. O 1 -x. FFx , AFe 2 As 2, RFe. As. O 1 -x x , Fe-1111 Fe- 122 Fe- Sr 4 AA 2 O O Fe As Sr 4 2 66 Fe 22 As 22 Fe -- 42622 Fe HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

EXPERIMENTAL INFORMATION Ceramic polycrystalline specimens of RFe. As. O 1 -x. Fx (R=Nd, Ce) were synthesized by G F Cheng and N. L. Wang at Institute of Physics, Chinese Academy of Sciences, Beijing Single crystals of AFe 2 As 2 (A=Ca, Ba, K) were synthesized at Ames National Lab. , Ames, USA and N. L. Wang Sr 4 A 2 O 6 Fe 2 As 2 (A=Sc, V) Oxypnictides polycrystalline specimens were provided by Hai-Hu Wen, from National Lab. Superconductivity, Beijing µSR performed by Uemura group in TRIUMF on some samples with participation of Julian Munevar and Dalber Sanchez Mössbauer experiments were performed at CBPF, Rio de Janeiro with an Oxford cryostat in sinusoidal mode with transmission geometry, with 57 Co: Rh source and sample at the same T HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Previous Studies RNi 2 B 2 C Mössbauer Spectroscopy in RNi 2 B 2 C and RNi. BC with 57 Fe at Ni site • information about local symmetry and magnetic order • Bhf at the 57 Fe nucleus, due to non collinear AF spin structure of the RE moments, acts as a pair-breaking field at the Ni site Tb. Ni 2 B 2 C T WF R C B Ni (Fe) TN c a b ü Magnetism is due exclusively to R magnetic moments: AF, FM, WFM, and SDW determined by coupling of R layers HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Superconductivity and Magnetism in Ho. Ni 2 B 2 C Reentrant behavior and incommensurate modulated magnetic structure for 4. 6 T 6 K Evidence of pair-breaking field at the Ni (57 Fe) D. R. Sánchez, H. Micklitz, M. B. Fontes, S. L. Bud’ko and E. Baggio Saitovitch, Phys. Rev. Lett. 76, 507 (1996) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

No Bhf field was observed at any temperature below TN for the AFM superconductors Er. Ni 2 B 2 C and Dy. Ni 2 B 2 C HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Structures of Fe-As: RFe. AO , AFe 2 As 2 and Sr 4 A 2 O 6 Fe 2 As 2 Sr 2(V/Cr)O 3 Fe. As Sr 2 AO 3 La. OFe. As - 111 Ba. Fe 2 As 2 - 122 Structure: Tetragonal P 4/nmm Tetragonal I 4/mmm Tetragonal P 4/nmm Structural transition: ~ 155 K ~ 140 K NONE Magnetic ordering: ~ 140 K 36 K Superconductor: with F dop & O deficiency withr K, Ca, Co doping A=V Local structure at Fe site is similar different Fe moments and 3 d Fe contribution in the density of states at EF level HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

La. OFe. As has structural distortion below ~150 K La. OFe. As has long range SDW-type AF order at ~134 K with Fe=0. 36 B HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Nd. OFe. As and Ce. OFe. As Nd. OFe. As Ce. OFe. As TS (P/4 nmm-Cmma) ~ 150 K ~158 K TN (Fe) ~ 141 K ~ 140 K ~ 0. 32 B ~ 0. 6 B ~ 2 K ~ 4 K Fe TN(R) Fratini M, Supercond. Sci. Technol. 21, 2008. Ying Chen, Phy. Rev. B 78, 2008. Y. Qiu, Phys. Rev. Lett. 101, 2008. Nd. Fe. As. O 1 -x. Fx and Ce. Fe. As. O 1 -x. Fx Electron-doping by F – substituting for O 2 - increases Tc to about 50 K. Nd Nd Ce G. F. Chen, Phys. Rev. Lett. 100, 247002 (2008) and Chin. Phys. Lett. HFI-NQI 25, 2235 (2008). Jun Zhao, Nature Materials 7, 953 CERN, (2008) Geneva 2010, 12 -17 September 2010

Nd. Fe. As. O 0. 88 F 0. 12 and Nd. Fe. As. O Room temperature MS RT Nd. Fe. As. O 0. 88 F 0. 12 spectrum: unique phase, similar to that found for La. OFe. As* EQ=0. 02(2) mm/s IS=0. 437(1) mm/s, RT Nd. Fe. As. O: small impurities, Fe. As (~ 8%) and Fe. As 2 (~5%). The main component (doublet) is attributed to Fe in Nd. Fe. As. O phase and their hyperfine parameters are almost the same as for Nd. Fe. As. O 0. 88 F 0. 12 *H. -H. Klauss et al. , Phys. Rev. Lett 101, 077005 (2008). HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Results for Nd. Fe. As. O The magnetic transition at ~ 140 K is due to the magnetic ordering of Fe moments. CM 1 : (I) = 90 ± 5 o, commensurate AF structure with the Fe spins lying in the (a, b) CM 2: (II) ≈ 55 o, all angles in the range 0 90 o occur with equal probability Below ~2 K an additional increase of Bhf, : transferred Bhf at Fe due to collinear AF order of Nd moments. ( EQ → measure of the As Tetrahedra) SR results* support our model used to analyze our Mössbauer spectra. HFI-NQI 2010, CERN, Geneva *A. 12 -17 Aczel, September et al. , Phys. Rev. 2010 B 78, 214503 (2008)

Results for SC Nd. Fe. As. O 0. 88 F 0. 12 Low temperature MS TC ~ 45 K No hyperfine magnetic field was observed at 57 Fe nucleus [B (1. 5 K) 0. 1 T] of Fe in hf superconducting Nd. Fe. As. O 0. 88 F 0. 12 at any temperature (down to 1. 5 K) Absence of magnetism in this compound HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Results for in Ce. Fe. As. O 1 -x. Fx Room temperature MS All spectra were fitted with single lines 4. 2 K MS The Bhf field at Fe nucleus decreases with F content and disappears for x=0. 16. Magnetism suppressed by F doping. HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Ce. Fe. As. O 1 -x. Fx phase diagram Neutron studies [13] Jun Zhao, et al. , Nature Materials 7, 953 - 959 (2008). Mössbauer results shown a region of coexistence of superconductivity and magnetism (phase separation). For Ce. OFe. As Fe ≈ 0. 39 B HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Results for Ce. Fe. As. O under applied external field MS with different T Ce moments order at ~5 K Beff ~ 12 T and 3 T Fe spins ordering at ~145 K lying in the (a, b) plane MS support the AFM ordering of Fe spins A fraction of Fe spins tend to align parallel (Beff ~ 12 T) and the remaining ones antiparallel (Beff ~ 3 T) to the external field Beff =Bext + Bhf HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

The Bhf in Nd. Fe. As. O and Ce. Fe. As. O can be associated to SDW AFM order of Fe spins below ~140 and ~145 K, as seen by neutrons The AFM ordering of Nd and Ce spins seen by neutrons at ~2 K and ~ 5 K generate additional Bhf No Bhf was observed at 57 Fe nucleus in Nd. Fe. As. O 0. 88 F 0. 12 and Ce. Fe. As. O 0. 84 F 0. 16 down 2 K Doping with F suppresses both the magnetic order and structural distortion in favor of superconductivity Fe magnetic moment estimated to be ~0. 35 B in Nd. Fe. As. O and ~0. 39 B in Ce. Fe. As. O. Similar to neutron data Coexistence (phase separation) of SC and magnetism has been observed in Ce. Fe. As. O 1 -x. Fx for 0. 05 x 0. 11. HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Ternary iron-arsenide Ca. Fe 2 As 2 - Structural transition (Tetr to orthorhombic) at ~ 170 K - Order of the Fe moments, in a commensurate AF structure. A. I. Goldman et al. , Phys. Rev. B 78, 100506 R (2008) *Pressure Induced Superconductivity in Ca. Fe 2 As 2. A. Kreyssig et al. , Phys. Rev. B 78, 184517 (2008) Milton S. Torikachvili et al. , PRL 101, 057006 (2008) SR T. Goko, Uemura, Sanchez, Saitovitch et al. Phys. Rev. B 78, 214503 (2009) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Ca. Fe 2 As 2 single crystal Mariella EQ=0. 207 mm/s IS=0. 44 mm/s =0. 26 mm/s φ ≈10 o Only one site at low T EQ=0. 339 mm/s Bhf= 9. 95 T Angle between Vzz and Bhf: ≈ 85 o 5 o Fe≈ 0. 66 B and lie in a-b plane (agrees with neutron results) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Ca. Fe 2 As 2 (T) Structural transition Jump in Bhf(T) at ~180 K, typical for a first-order transition commensurate AFM ordering with Fe spins lying in the (a, b) plane HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Vzz in Ca. Fe 2 As 2 was found to be parallel to c. Only one Fe site showing a first order transition at ~ 140 K with the Fe spin lying in the (a, b) plane Hole doped AFe 2 As 2 (with K or Na) shows a phase separation at low temperature with a fraction of Fe ions in a paramagnetic state while remaining ones have a magnetic moment reduced related to undoped, order magnetically TO > Tc. This two phases are indistinguishable at room temperature Same behavior is observed for Co doped Ba. Fe 2 As 2 with the difference that in this case the doping is being performed at the Fe site In all the cases the doping distribution seems not to be homogeneous HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Sr 4 A 2 O 6 Fe 2 As 2 Iron Pnictides (so-called 42622), with a perovskite layer between Fe. As layers, - No SDW ordering No structural transition Large Fe-Fe interlayer distances (~15 Å) - TC= 37 K for Sr. VOFe. As - 0. 1 T transferred field to Fe in Sr. VOFe. As - No SDW in Sr. Sc. OFe. As M. Tegel et. Al, Zeitschrift fur anogarnische und allgemeine Chemie, V 635, 2242 (2009) X. Zhu et. Al, Physical Review B 79, 220512(R), (2009) Y. L. Xie et al, Europhysics Letters 86, 57007 (2009) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Sr 4 V 2 O 6 Fe 2 As 2 δ=0. 297(2) mm/s ΔEQ=0. 256(2) mm/s μSR show strong static magnetism below 100 K, increasing volume fraction for low temperature HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Possible coexistence of magnetic ordering in V atoms and superconductivity in Fe. As layers in Sr. VOFe. As Magnetic ordering found for Sr. Sc. OFe. As does not correspond to SDW or incommensurate magnetic ordering HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Perspectives for Mössbauer in the studies of Unconventional SC Follow details at local level of magnetic transitions Determine the structural phase transition and any special related feature HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

Thank you FAPERJ, Pensa Rio, Infra estrutura , Cientista do Estado PRONEX, CNPq (CIAM, DFG) CAPES (PROBRAL) HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

TEAM Elisape Baggio Saitovitch Magda Bittencourd Fontes Marcos de Castro carvalho Pesquisador Titular III (CNPq – 1 A) Pesquisador Associado III Mestre Tecnologista PESQUISADORES VISITANTES ESTRANGEIRO Manfred Forker Hans Micklitz CNPq POS DOUTORANDOS Eduardo Hering Novaes Mariella Alzamora Camarena Urbano Miguel Tafur Tanta Scheilla Maria Ramos da Silva Willian Alayo Rodriguez Yutao Xing FAPERJ CLAF-CNPq /CNPq PNPD CNPq FAPERJ/PCI-CNPq ALUNOS DE DOUTORADO Isabel Dinola Julian Munevar Cagigas Justiniano Quispe Marcatoma Kumaresavanji Malaivelusamy William Trujillo Herrera Mestre FAPEAM CNPq BID CNPq-TWAS CLAF-CNPq ALUNOS DE MESTRADO Ury Denver Chacón Hernandez CNPq HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva

We are looking for Pos docs to work in: Mossbauer, PAC, magnetization and transport under pressure BRAZILIAN CENTER FOR RESEARCH IN PHYSICS- CBPF / MCT www. cbpf. br Magnetic Multilayer, SC, Oxides, Heavy Fermions! Magnetic Multilayer, SC, Oxides, Heavy Fermions elisa@cbpf. br HFI-NQI 2010, 12 -17 September 2010 CERN, Geneva