“Molecular Magnetism”: What is it? What it is NOT! or “What I wish I knew when I was in your seat….” Mark W. Meisel and Group Members (past and present) Department of Physics and NHMFL, University of Florida Long-standing collaboration with Daniel R. Talham and his Group Department of Chemistry, University of Florida Start with a Definition: (but avoid blathering….. on…. and…. on…. and….on….) A short history of molecular magnetism http://www.unizar.es/magmanet/magmanet-eu/index.php?/short_history_of_molecular_magnetism.html

Molecular Magnetism Web: a gate to molelcular magnetiem (http://www.molmag.de) thanks to Jürgen Schnack or is it Molecule-based Magnetism? (don’t trust Wikipedia….) Supported by the National Science Foundation DMR-1202033 (MWM), DMR-1405439 (DRT), DMR-1157490 (NHMFL), and the UF Center for Tomorrow’s Materials (Today!)

C. M. Hurd, Contemp. Phys. 23, 469-493 (1982)

not comprehensive? where is: weak ferromagnetism, canted antiferromagnetism, …

Date: 1564 Title: Floridae Cartographer: Jacques Le Moyne de Morgues

http://scholar.library.miami.edu/floridamaps/first_spanish_period.php

An extra functionality dimension from ionic activity.The usual control parameters for tuning the functionality of complex oxides—electric field E, which controls polarization P; magnetic field H, which controls magnetization M; and stress σ, which controls strain ɛ (A)—should be augmented (B) by the chemical potential µ to capture the functionalities driven by mobile ions and defects in these materials (as described by the concentration of mobile species, c).

S V Kalinin, and N A Spaldin Science 2013;341:858-859 Published by AAAS

The Art of Making a Good and Tasty Sandwich (culinary heterostructure) ABA heterostructure

ABCBA heterostructure A

A B

B

salami

A

C

salami A+B+A= A

Chren pikantné (Armoracia rusticana)

A+B+C+B+A= B

B

A

The Art of Making a Good and Tasty Sandwich (culinary heterostructure)

Thin bread Patina of strong mustard Thick salami Patina of strong mustard Thin bread

A+B+C+B+A=D D is new and dominate taste!

http://newyork.seriouseats.com/2010/10/ a-sandwich-a-day-fried-salami-at-eisenberg-sa.html

Recipe is same for nanostructures where interfaces are important!

Alphabet Soup and Some Possible Recipes

Spin Crossover (SCO) S LS

S HS + Electron Transfer =

Charge Transfer Induced Spin Transition (CTIST) S1 = 0 and S2 = 0 S1 = 1/2 and S2 = 3/2 (“cooperative”, e.g. lattice distortion too)

Light-Induced Excited Spin State Trapping (LIESST)

M=

χ

χ

=

B C T

χT

Temperature

Talham – Meisel Chemistry-Physics Group Retreat Aug. 2014

Switching magnetism with light above 77 K in a bistable coordination polymer heterostructure

1.0 0.8

hν

Dark Light

B = 100 G

-5

Magnetization [10 emu G]

Olivia N. Risset, Tatiana V. Brinzari, Marcus K. Peprah, Pedro A. Quintero, Mark W. Meisel, Daniel R. Talham, preprint

CoFe@CrCr core@shell nanoparticles

0.6 0.4 0.2 100

scale bar = 200 nm

150 200 250 Temperature [K]

300

PAQ and MKP: PhD theses (2015)

Prussian Blue and Analogs: Magnetism

man-made pigment from early 1700’s

D. Davidson, L.A. Welo, J. Phys. Chem. 32 (1928) 1191. J. Richardson, N. Elliott, J. Am. Chem. Soc. 62 (1940) 3182. N. Holden, B. T. Matthias, P. W. Anderson, H. W. Lewis, Phys. Rev. 102 (1956) 1463. R.M. Bozorth, H.J. Williams, D.E. Walsh, Phys. Rev. 103 (1956) 572. A. Ito, M. Suenaga, K. Ono, J. Chem. Phys. 48 (1968) 3597. H.J. Buser, D. Schwarzenbach, W. Petter, A. Ludi, Inorg. Chem. 16 (1977) 2704. [x-ray structure of Fe4[Fe(CN)6]3 • xH2O] P. Day, F. Herren, A. Ludi, H. U. Gudel, F. Hulliger, and D. Givord, Hel. Chim. Acta 63 (1980) 148. Reviews: K. Dunbar and R.A. Heintz, Prog. Inorg. Chem. 45 (1997) 283. M. Verdaguer and G.S. Girolami, “Magnetic Prussian Blue Analogs,” in Magnetism: Molecules to Materials 5 (Wiley-VCH, 2004) 283.

Persistent Photoinduced Magnetism (PPIM) “Powders*”: O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto, Science 272 (1996) 704 “Perspective”: M. Verdaguer, Science 272 (1996) 698

Dark

Irradiated

Fe3+

Magnetization (arb. units)

20

S=3/2

S=1/2

T < TC

S=1

Co2+

C-N

eg t2g

10.3 Å

15 10.0 Å Fe2+ S=0

10

-20

0

C-N

S=0

S=0

20

Time (Min)

40

Co3+

eg t2g

* (K0.2Co1.4[Fe(CN)6] · 6.9 H2O) Slide from J.-H. Park

5

5.0

4

4.5

2

 (10 emu/cm )

3 2

-5

-5

2

 (10 emu/cm )

K0.2Co1.4[Fe(CN)6]·6.9H2O

1 0

N-C

Co

Fe

K

H2O

3.5 3.0 2.5

0

C-N

4.0

10 20 T (K)

30

0.0

0.5 time (hours)

1.0

Persistent Photoinduced Magnetization O. Sato et al., Science 272, 704 (1996). Slide from D.M. Pajerowski

5

5.0

4

4.5

2

 (10 emu/cm )

3 2

-5

-5

2

 (10 emu/cm )

K0.2Co1.4[Fe(CN)6]·6.9H2O

1 0

N-C

Co

Fe

K

H2O

4.0 3.5 3.0 2.5

0

C-N

T=5K

10 20 T (K)

30

0.0

0.5 time (hours)

1.0

Persistent Photoinduced Magnetization O. Sato et al., Science 272, 704 (1996). Slide from D.M. Pajerowski

B A

100nm

… photocontrolled magnetism that is stable (> weeks) to high temperatures. A + B + A = D (“metamaterial”) aka “Magnetolomics”

Dark state

15

FC in 100 G

Light state 8.0

10

Light on 7.5 7.0

5

6.5

T = 60 K

0 1 2 Time (hours)

0 1.0 0

20 Heterostructure 40 60 80 Temperature (Kelvin)

0.8

MAX

A

Magnetic response (arb. units)

Heterostructures of molecule-based magnets yield ….

0.6 0.4 0.2 Single phase

Pajerowski et al., J. Am. Chem. Soc. 132 (2010) 4058

0.0 0

20

40

60

Temperature (K)

80

Persistent Photocontrolled Magnetism (PPCM) in Nanoscaled Heterostructures of Prussian Blue Analogs (Prussian blue: man-made pigment from 1704) ≈10 nm shell

A Ni-Cr

B

A

B

C

B Co-Fe A Reproducible Tasty Properties!

100nm

Films: Pajerowski et al., J. Am. Chem. Soc. 132 (2010) 4058

Films with “spin crossover” (Fe-Pt SCO) material Gros et al., J. Am. Chem. Soc. 136 (2014) 9846

New Ingredient… same Tasty Properties!

Core@Shell: Dumont et al., Inorg. Chem. 50 (2011) 4295

Core@Shell: C = Co-Cr Risset et al., J. Am. Chem. Soc. 136 (2014) 15660

Mechanism? Irradiation with white light relaxes interface strain induced while cooling, causing rearrangement of magnetic moments near the interface. Insight from Ni-Cr single component films studied by EPR at NHMFL. Pajerowski et al., Phys. Rev. B 82 (2010) 214405

Ingredient 1: Photoactive Component: CoFe Prussian Blue analogue (PBA)

Rbj Cok [Fe(CN)6]l • n H2O (variables are j , k , l , n )

FCC lattice

M. Verdaguer, Science 272 (1996) 698

Defects in structures are a level of Complexity!

Fe3+ Co2+

Rb+

H2O replaces CN ligand leaving a Fe vacancy.

H2O CN-

Rb sits in an interstitial site. (and “charge balance”!)

Note M-CN-M’ bridging!

High Spin 50 K

Co/Fe = 1.5

350 K

Co/Fe = 1.37

CTIST: Charge Transfer Induced Spin Transition (HS to LS by cooling)

Co/Fe = 1.32

5 Co/Fe = 1.26

0 Co/Fe = 1.15

Low Spin

T vs. T plots

Shimamoto, Ohkoshi, Sato, Hashimoto, Inorg. Chem. 41 (2002) 678

Ingredient 2: Ferromagnetic Component: NiCr Prussian Blue analogue (PBA) J.-H. Park, Ph.D. thesis (2006) Univ. of Florida

HetroStructured Layered Film : Co-Fe / Ni-Cr (CN)6 A

4

0 1

~ 10 Å

B

2

3

A

A: Photoinduced Magnet Co

Fe

~

Ni

Cr

Ni-Cr Co-Fe Ni-Cr Co-Fe

B: High TC Magnet B A B A

A+B=? High TC Photoinduced Magnet ?

Ideas motivated by: M. Nishino, Y. Yoshioka, K. Yamaguchi, Chem. Phys. Lett. 297 (1998) 51 Slide from J.-H. Park

Long-Range vs. Short-Range Ordering Magnetic Coherence Length: ξ (T, spatial/spin dimensions, …) Characteristic Length of Scale of Sample: (“structural coherence length”)

ℓ

ℓ < ξ : Short-Range “Order”

ℓ ξ

ℓ~ξ:

ℓ ξ

(“spin liquid”): Interactions/correlations at short distances Fingerprints: Curie or Curie-like  with no TC , ... “Intermediate Order” :

Fingerprints: 0 < Tc < Tc(bulk), ...

ℓ > ξ : Long-Range “Order”

(“spin solid”): Interactions/correlations at long distances Fingerprints: “bulk” TC , Coercive Magnetic Field, … Curie-Weiss Law:  =

_ C_ T+ Θ

ℓ ξ

A B 100nm

Extra Important Points: White Light (vs monochromatic)

15

Light state 8.0

10

Light on 7.5 7.0

5

6.5

smaller lengths: N. Dia et al., Inorg. Chem. 52 (2013) 10264 M. Presle et al., J. Phys. Chem. C 118 (2014) 13186

T = 60 K

0 1 2 Time (hours)

0 1.0 0

Lengths ≳ 50 nm

other morphologies: D.M. Pajerowski, PhD thesis (2010)

Dark state

20 Heterostructure 40 60 80 Temperature (Kelvin)

0.8

MAX

A

Magnetic response (arb. units)

Result 1: Thin films ABA (NiCr-CoFe-NiCr) Prussian Blue analogues (PBA)

0.6 0.4 0.2 Single phase 0.0 0

20

40

60

80

Temperature (K) D.M. Pajerowski et al., J. Am. Chem. Soc. 132 (2010) 4058

Result 2: CoFe@NiCr-PBA core-shell nanoparticles

Control of the Nucleation

NiIICl2 K3CrIII(CN)6

RbCoFe PBA KNiCr PBA

Low concentration (add very slow…)

200nm

CoIICl2 K3FeIII(CN)6

Multilayered Heterotructure

(10 x the excess of Cores vs. precursor)

Slide from M.F. Dumont

Result 2: CoFe@NiCr-PBA core-shell nanoparticles Mechanism and Extent of Interface Strained Region ~ 80 nm shell

~ 100 nm shell dark light 0H = 100 G

120

3

3

80

20

0 0

20

40

60

40

100 50 0

0

20

T (K)

40

60

0

80

30

30

30

 (cm / molCoFe)

40

20

3

10 dark - light 0H = 100 G 0

20

40

T (K)

10 dark - light 0H = 100 G

0 60

80

60

80

60

80

20

3

 (cm / molCoFe)

40

20

40

T (K)

40

0

20

T (K)

3

 (cm / molCoFe)

150

0

80

dark light 0H = 100 G

200

 (cm / molCoFe)

40

~ 160 nm shell 250

 (cm / molCoFe)

dark light 0H = 100 G

3

 (cm / molCoFe)

60

0

20

40

T (K)

10 dark - light 0H = 100 G

0 60

80

0

20

40

T (K)

E.S. Knowles et al., Polyhedron 66 (2013) 153; E.S. Knowles, Ph.D. thesis (2013)

Result 3: CoFe@CoCr-PBA core-shell nanoparticles (Change of Ingredient) Mechanism and Extent of Interface Strained Region Light-Induced Changes in Magnetism in a Coordination Polymer Heterostructure … Olivia N. Risset, Pedro A. Quintero, et al., J. Am. Chem. Soc. 136 (2014) 15660.

Interfaced Strained Region (ISR) extends to about 25 nm in Shell.

Thickness of Shell influences Core and ISR and Domain rearrangement.

Ingredient 1: Photoactive Component: Spin-crossover (SCO) Hofmann-like framework (Change of Ingredient) a c

~ 300 K

Fe(azpy)[Pt(CN)4]

S=0

S=2

Light-Induced Excited Spin State Trapping = LIESST HS LS Δ (HS→LS)

a (Å) c (Å) Volume (Å3) Fe-Neq (Å) Fe-Nax (Å) 7.41 ± 0.02 13.37 ± 0.05 734 ± 4 ----------7.16 ± 0.04 12.98 ± 0.03 665 ± 6 ----------0.25 ± 0.04 0.39 ± 0.06 69 ± 7 0.18 ± 0.03 0.20 ± 0.03

Agustí et. al. Chem. Mater. 2008, 20, 6721

Result 4: Films of SCO Fe-Pt and NiCr-PBA (Change of Ingredient) Light-Induced Magnetization Changes in a Coordination Polymer Heterostructure … Corey R. Gros, Marcus K. Peprah, et al., J. Am. Chem. Soc. 136 (2014) 9846.

SCO Fe-Pt NiCr-PBA

Glass

Result 5: Platelets of SCO Fe-Ni and NiCr-PBA (Change of Ingredient) NiCr-PBA/Fe(azpy)[Ni(CN)4] : Marcus K. Peprah, Corey R. Gros, et al., in preparation

Result 6: CoFe@CrCr-PBA nanoparticles (Change of Ingredient) Switching magnetism with light above 77 K in a bistable coordination polymer heterostructure Olivia N. Risset, Tatiana V. Brinzari, Marcus K. Peprah,Pedro A. Quintero, Mark W. Meisel, Daniel R. Talham, preprint

1.0 0.8

hν

Dark Light

B = 100 G

-5

Magnetization [10 emu G]

Early attempts and hints: Elisabeth S. Knowles, Ph.D. thesis (2013)

CoFe@CrCr core@shell nanoparticles

0.6 0.4 0.2 100

scale bar = 200 nm

150 200 250 Temperature [K]

300

Now Persistent Magnetism changes thermally compromised by CoFe-PBA electron relaxation. Can the Interface Strained Region magnetic domains possess memory to CrCr-PBA TC = 220 K?

High Spin 50 K

Co/Fe = 1.5

NaxCoy[Fe(CN)6]z •nH2O

350 K

5K

350 K

Co/Fe = 1.37

Co/Fe = 1.32

5 Co/Fe = 1.26

0 Co/Fe = 1.15

Low Spin

T vs. T plots

T vs. T plots

Shimamoto, Ohkoshi, Sato, Hashimoto, Inorg. Chem. 41 (2002) 678

Persistent Photocontrolled Magnetism (PPCM) in Nanoscaled Heterostructures of Coordination Polymers [PBA = Prussian blue analogue] A NiCr-PBA

B

B

A

C

B CoFe-PBA

Films: Pajerowski et al., J. Am. Chem. Soc. 1 132 (2010) 4058

Films with “spin crossover” Fe-Pt SCO / NiCr-PBA Gros et al., J. Am. Chem. Soc. 4 136 (2014) 9846

New Ingredient… same Tasty Properties!

5

Fe-Ni SCO / NiCr-PBA

Core@Shell: Dumont et al., Inorg. Chem. 2 50 (2011) 4295

6 Core@Shell: CoFe@CrCr-PBA adding external pressure… add chemical tuning… Road to 300 K?

7

Core@Shell: C = CoCr-PBA Risset et al., JACS 3 136 (2014) 15660

1.0 0.8

Dark Light

hν

B = 100 G

-5

Reproducible Tasty Properties!

100nm

Magnetization [10 emu G]

A

CoFe@CrCr core@shell nanoparticles

0.6 0.4 0.2 100

150 200 250 Temperature [K]

scale bar = 200 nm

300

Date: 1564 Title: Floridae Cartographer: Jacques Le Moyne de Morgues

http://scholar.library.miami.edu/floridamaps/first_spanish_period.php

Join the Exploration! Learn the ABCD’s: Always Be Collecting Data F3: Form Follows Function SOC: Spin Orbit Coupling

Think and Do! We are colleagues!

Now some “canned” slides for potential questions.

Magnetic anisotropy in thin films of Prussian blue analogues

Phys. Rev. B 82 (2010) 214405 Phys. Rev. B 82 (2010) 214405

D.M. Pajerowski, J.E. Gardner, M.J. Andrus, S. Datta, A. Gomez, S.W. Kycia, S. Hill, D.R. Talham, M.W. Meisel

116 GHz

Rb0.8Ni [Cr(CN)6]0.7·nH2O

Demagnetizing Factors!

External Pressure tuning of the Magnetic Response in CoFe-PBA

[ Mdark (T) - Mlight(T) ] / Mdark(T = 300 K)

Result 7: CoFe@CrCr-PBA nanoparticles (Light and Pressure) (Change of Environment)

0.12

September 2014 MP163: 109BC1-2 : CoFe@CrCr White Light (no filter) FC in 100 G, 0H = 100 G

P = 2.55 GPa irradiation at 80 K

0.10

Optical Presssure Probe 2.0

0.08

CoFe-PBA TCTIST

0.06

CrCr-PBA TC Bulk

0.04

Domain distortion in CrCr-PBA persists to Tc, which is Pressure Depedent.

0.02

0.00

100

150

200

Temperature (K)

250

300

Z. Mitróová et al., Acta Phys. Pol. A 133 (2008) 469

APS – ANL data under analysis… A. Felts et al. 10.4 Å 10.3 Å 10.0 Å

E.S. Knowles, Ph.D. thesis (2013)

Laure Catala and Talal Mallah and coworkers

Small (< 30 mn) core@shell CoFe-PBA@NiCr-PBA: Linkage Isomerism? (unpublished)

M. Verdaguer and G.S. Girolami (2004): “The solid Prussian blue analogues can also suffer from one or more of the following problems: (4) Linkage Isomersism” Time, strain, interface… Irreversible / Reversible “High pressure neutron scattering of the magnetoelastic Ni-Cr Prussian blue analogue,” D. M. Pajerowski, S. E. Conklin, J. B. Leão, D. Phelan, L. W. Harriger, Phys. Rev. B 91, 094104 (2015)

(and untold story of route to T > 200 K)

CAB

1.0

dark light 0H = 100 G

-3

M (10 emu G)

High-TC core-shells?

1.5

0.5

0.0 0

CoFe-PBA

50

100

150

200

250

300

T (K)

NiCr-PBA CrCr-PBA

-5

A

M (10 emu G)

4

*heterogeneous (“chunks” of B in sample)? E. S. Knowles et al., unpublished.

dark light 0H = 100 G

3 2 1 0 50

100

150

200

T (K)

250

300

Photoinduced Magnetism in Cobalt-Iron Cyanide O. Sato, Y. Einaga, A. Fujishima, K. Hashimoto, Inorg. Chem. 38 (1999) 4405. T. Kawamoto, Y. Asai, S. Abe, Phys. Rev. Lett. 86 (2001) 348. (ab initio quantum cluster calculations)

Diamagnetic Ferrimagnetic

FeII(LS, S = 0) – CN - CoIII(LS, S = 0) FeIII(LS, S=1/2) – CN - CoII(HS, S=3/2)

“Hunch”: distribution of energy barriers exist due to local environment.