Crystal Structure Determination and physical properties of Molecule-Based Multiferroic Materials

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1 Crystal Structure Determination and physical properties of Molecule-Based Multiferroic Materials Lidia mazzuca All you need is neutron season 2 1

2 General Introduction Multiferroics and MOFs OUTLINE Previous work : [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (HCOO) 6 ] n Nuclear and Magnetic structure [NH 2 (CH 3 ) 2 ] n [Fe III Co II (HCOO) 6 ] n and [NH 2 (CH 3 ) 2 ] n [Fe III Mn II (HCOO) 6 ] n X-ray and Neutron Multipattern Nuclear and Magnetic structure (neutron experiments) Conclusion 2

3 What are Multiferroic materials? Multiferroics : Compounds with more than one ferroic order in a single phase Electric Order Magnetic Order Multiferroic material 3

4 Multiferroics TYPE I TYPE II Ferroelectricity and ferromagnetism have different sources and are independent Weak coupling Different transition temperature High polarization (for ferroelectrics) 4 Ferroelectricity and ferromagnetism strongly coupled Electric order at low temperatures Low polarization (for ferroelectrics) Magnetic order causes ferroelectricity; magnetic (electric) moment can be changed by electric (magnetic) field

5 Applications New multifunctional materials Ultra-sensitive solid state magnetic sensors Computer memory Storage and magnetic read/write... 5

6 Multiferroic Metal Organic Framework Classical Magnets High Density Close Packed Opaque Molecular Magnets Metal center Organic ligand Co-ligand/cation Low Density Transparent Cristalline 6

7 Magnetic structures Magnetic structures defined by: - Propagation vector(s) - Moment magnitude(s) - Moment direction(s) Nuclear Interaction : Interaction between the neutrons and the nuclei of the ions Magnetic Interaction: Interaction between the magnetic moment of the neutron with the spin and orbital magnetic moments of the unpaired electrons in the solid 7

8 Case study Crystal and Magnetic Structural Neutron investigation in mixed valence : [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (HCOO) 6 ] n framework 8

9 [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (HCOO) 6 ] n Multiferroic MOF system Fe(III) Formate ligand P -31c a (Å)= (12) b (Å)= (12) c (Å)= (3) Crystal network: magnetic properties Fe(II) Guest-molecule: electric properties, disordered at HT Dimethylammonium counterion L. Cañadillas-Delgado et al. JACS (2012) 9

10 Heat capacity as function of temperature 4.8 K 155 K 37 K 10

11 [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (HCOO) 6 ] n P -31c Room Temperature Low Temperature R-3c a (Å)= (12) b (Å)= (12) c (Å)= (3) Phase transition 155K a (Å)= (17) b (Å)= (17) c (Å)= (8) 11

12 [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (HCOO) 6 ] n Dielectric measurement 155 K Antiferroelectric Paraelectric Structural phase transition 12

13 D1B diffractometer Magnetic measurement Increase of Bragg reflection (100) Indexed with K=(0,0,0) 100 Magnetic phase transition 37 K 13

14 [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (HCOO) 6 ] n 120º 120º 120º Fe(II): Component along c axis + component in ab plane Fe(III): Strictly along c axis

15 Case study Case study X-ray and Neutron Magnetic Structural investigation in mixed valence : [NH 2 (CH 3 ) 2 ] n [Fe III Co II (HCOO) 6 ] n and [NH 2 (CH 3 ) 2 ] n [Fe III Mn II (HCOO) 6 ] n Frameworks 15

16 Phases of our work in few steps Replacing the divalent Fe II ions for Co II or Mn II Single crystal X-ray diffraction Squid Magnetometry Structure refinement at 45K combining X-ray and High resolution neutron diffraction using a Multipattern approach Magnetic structures determined by difference patterns between paramagnetic and magnetically-ordered regions 16

17 X-Ray experiment at the Soleil Synchrotron facility Co II /Mn II -Fe III Data were indexed, integrated using Crysalis Pro software Final R indices [I > 2σ(I)]: R1/wR2= / λ = Å The structures were solved by direct method using SHELXS 17 T=45K P -31c a (Å)= b (Å)= c (Å)=

18 NEUTRON experiment D2B High resolution P -31c T=45K Multipattern approach using FullProf λ = Å Hydrogen atoms determined 18

19 P -31c a (Å)= b (Å)= c (Å)= NO STRUCTUTRAL PHASE TRANSITION for Co(II)Fe(III) and Mn(II)Fe(III) WHY??? Ordering for Fe(II) compound Reorientation Mn(II)/Co(II) compounds 19

20 Magnetometer measurements of isostructural [NH 2 (CH 3 ) 2 ] n [Fe III M II (HCOO) 6 ] n Fe(II)Fe(III) Mn(II)Fe(III) Co(II)Fe(III) 20

21 NEUTRON experiment D1B High Flux (100) λ =2.521 Å Propagation vector K = (0,0,0) Fe II Fe III Mn II Fe III (100) (002) (101) (100) (002) (101) Co II Fe III 21

22 How to determine the MAGNETIC model? Multipattern approach for well defined structural model -(FP) Determine K-propagation vector- (K- Search) Performs symmetry analisys- BasIreps (Fullprof) Introduce and refine by LSQ the magnetic phase (FP) and Structure solution by Sann (FP) INPUT Peak positions of Magnetic reflections Cell parameters k vector Atomic positions Space group Irreducible representations Extracted integrated intensities 22

23 Representational analysis BasIreps (Fullprof) 6 possible Irreps Γ 1- Γ 6 Possible arrangement of magnetic structure Γ 1 to Γ 4 are real and one dimensional Γ 5 and Γ 6 have an imaginary part and are two dimensional BUT Propagation vector K = (0,0,0) consequently the Fourier coefficients must be real Γ 1 to Γ 4 are possible solutions p Γ3 23

24 Position of atom j in unit-cell l is given by: where R l is a pure lattice translation 24

25 The magnetic moment m lj associated with the atom j at the unit cell with origin in R l, is determined by the Fourier series: Where S kj are the Fourier components (linear combination of Basis vectors of irreps) with propagation vector k corresponding to the atom j in the zero th unit cell. For getting m lj as real vectors S* kj = S -kj should be satisfied 25

26 [NH 2 (CH 3 ) 2 ] n [Fe III Co II (HCOO) 6 ] n Global AF coupling in ab-plane The Co(II) magnetic moments produce a ferrimagnetic behaviour along c-axis 26

27 [NH 2 (CH 3 ) 2 ] n [Fe III Mn II (HCOO) 6 ] n Global AF coupling in ab-plane The Mn(II) magnetic moments produce a small ferromagnetic component along c-axis due to spin canting 27

28 Conclusion From [NH 2 (CH 3 ) 2 ] n [Fe III M II (HCOO) 6 ] n (where M= Co(II) or Mn(II) ) isostructural compounds 1. Crystal structures have been refined combining High resolution neutron diffraction with synchrotron X-ray diffraction at 45K using a multipattern approach 2. Dimethylammonium hydrogen atoms have been localized 3. We did not observe any occurence of phase structural transition = No electric order = no multiferroic 4. Using neutron diffraction we observed that: i. The magnetic structure of Co(II) consist in a non compensated AFM arrangement where the magnetic moments are contained in ab plane so similar to Fe(II) compound ii. Moreover for Mn(II) compound is almost AFM in ab plane with a small spin canting together with a no compensation along c-axis which produce ferromagnetic order 28

29 OUTLOOK To investigate multiferroic materials from the same family of [NH 2 (CH) 3 ] n [Fe III M II (HCOO) 6 ] n, compounds, with different metal ions and/or different co-ligands. In order to understand the magnetic structure observed and the role of dimethylammonium in the cavity we submitted a proposal for neutron diffraction experiments under pressure conditions We are collaborating with the group of Dr. Silvia Picozzi from CNR SPIN (Italy) in order to obtain Ab initio DFT calcution to rationalize the described magnetic structures 29

30 THANK YOU FOR YOUR ATTENTION! 30

31 Acknowledgements and References Oscar Fabelo Alberto Rodríguez-Velamaza n Juan Rodríguez-Carvajal 1. R. J. Kuppler, D. J. Timmons, Q.-R. Fang, J.-R. Li, T. A. Makal, M. D. Young, D. Yuan, D. Zhao, W. Zhuang, H.-C. Zhou, Coordination Chemistry Reviews, 2009, 253, L.Can adillas-delgado, O.Fabelo,J. A.Rodríguez-Velamaza n, M.H.Leme e-cailleau, S.A. Mason, Hagen, K. S.; Naik, S. G.; Huynh, B. H.; Masello, A.; Christou, G., J. Am. Chem. Soc. 2009, 131, Zhao, J.-P.; Hu, B.-W.; Lloret, F.; Tao, J.; Yang, Q.; Zhang, X.-F.;Bu, X.-H., Inor. Chem. 2010, 49 (22), E.Pardo,F. Lloret,J.-P. Zhao,X.-He Bu, Vi.Simonet,C. V. Colin, and J. Rodríguez-Carvajal, J. Am. Chem. Soc., 2012, 134 (48), pp Aoyama T, Yamauchi K, Iyama A, Picozzi S, Shimizu K, Kimura T, Nature Comm ,