Neutron Scattering studies of the Crystal and 

Magnetic Structures of Molecular Magnets

Danielle Villa

Mentors: Craig Brown and Qingzhen Huang 
Molecular Magnets

 Molecular Quantum Magnets

 Molecules that exhibit magnetic behavior at low temperatures

 Antiferromagnetism

 H=∑D(Si) + ∑ J

i,jSi

·Sj

 D-> Single Ion Anisotropy

 J-> Magnetic Exchange Interaction

 Quantum Theory

 Information Storage

 Quantum Computing

^ ^ ^ ^
Neutrons

Neutron Scattering “LECTURE 1: Introduction & Neutron Scattering “Theory”” by Roger Pynn

“Dynamics and Neutron Scattering” by John R.D. Copley
Neutron Scattering

Diffraction Inelastic

BT-1 High Resolution Powder Diffractometer Disk Chopper Time of Flight Spectrometer
Powder Diffraction

Basic Solid State Chemistry by Anthony R West (pg. 164)

https://en.wikipedia.org/wiki/X-ray_crystallography

Structure from Ki Min Nam, et al. J. Am. Chem. Soc., 2012, 134 (20), pp 8392–8395
CoCl2pyz2

 S = 3/2

 Orthorhombic

 TN = 0.8 K
Unpublished Data

Fit by Qingzhen Huang
Inelastic Scattering

Neutron Scattering—A Non-destructive Microscope for Seeing Inside Matter

By Roger Pynn
NiX2

(pyz)2

NiCl2(pyz)2 NiBr2

(pyz)2

 S=1

 Tetragonal

 S=1

 Tetragonal
NiX2

(pyz)2

Pyrazine

Single Layer Unit Cell
NiX2

(pyz)2

NiCl2(pyz)2 NiBr2

(pyz)2

 S=1

 Tetragonal

 S=1

 Tetragonal
C

p (Jmol

-1K

-1

)

Long Range Magnetic Order

• NiBr2

•TN = 1.9 K

•NiCl2

•TN < 0.08 K

Temperature (K)

J. Liu, et al. Inorg. Chem. 2016, 55, 3515−3529
NiBr2pyz2

➢S=1

➢Tetragonal

➢TN=1.9 K

Single Layer
J=0.09 meV D=-0.009 meV J’=0.04 meV

J=0.09 meV D=0 meV

J=0.09 meV D=0 me V J’=0.04 meV J=0.099 meV D=-0.0009 meV J’=.04 meV

J=0.09 meV D=0 meV J’=0.02 meV
A Need
Thank You  Qingzhen Huang  Craig Brown  Jamie Manson  Joe Dura  Julie Borchers  Dan Neumann  Steve Disseler  William Ratcliff

 Juscelino Leao  YegorVekhov  Alan Ye  Terry Udovic  Jeff Lynn  Yamali Hernandez  Jamie Brambleby  Paul Goddard
Non-NIST Experimental Partners

 The University of Warwick

 Advanced Photon Source, Argonne National Laboratory

 National High Magnetic Field Laboratory, Los Alamos National Laboratory

 Swiss Muon Source, Paul Scherrer Institut

 ISIS Pulsed Neutron and Muon Source
Software Used for Data Analysis

 Neutron Diffraction

 CMPR

 GSAS

 Inelastic Neutron Scattering

 DAVE

 SpinW

 Visualization

 VESTA
CoCl2pyz2

Comparison: Sample without Vaseline

0 1 2 3 4 5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

T = 2 K

T = 5 K M (B/Co2+

) 0H (T)

0 1 2 3 4 5

0.0

0.5

1.0

1.5

2.0 T = 2 K

T = 5 K M (B/Co2+

) 0H (T)

0 100 200 300

0

2

4

6

8

10

0H = 0.1 T Curie-Weiss Fit 230  T  300 K

  eff = 4.61(3)  B 

CW = −2.96+4.0-2.2 K mol (10

6 m-3 mol)  ()

0 50 100 150 200 250 300

0

1

2

3

4

5

6

7

8

0H = 0.1 T mol (10-6 m3 mol-1)  ()

0 50 100 150 200 250 300

1.0

1.5

2.0

2.5

3.0

3.5

0H = 0.1 T

molT (10-5 m3 K mol-1)  ()

1 10 100

0

1

2

3

4

5

d(molT)/dT (arb. units)  ()

1 10 100

1.0

1.5

2.0

2.5

3.0

3.5

0H = 0.1 T

molT (10-5 m3 K mol-1)  ()

1 10 100

0

1

2

3

4

5

6

7

8

0H = 0.1 T mol (10-6 m3 mol-1)  ()

JLM4-088: CoCl2(pyz-D4)

2 Sample dispersed in Vaseline



NiBr2pyz2

1 10 100

0.0

0.5

1.0

1.5

2.0

2.5

1 10 100

1.5

2.0

2.5

3.0 Effective Moment (B

)

T (K)

 NiCl2(pyz)2 (1)

 NiBr2(pyz)2 (2)

 Ni(NCS)2(pyz)2 (3)

 (10-6 cm

3/mol)

T (K)

(a)

(b)





0 5 10 15

0.0

0.5

1.0

1.5

2.0 Magnetic Moment (B/Ni)

Magnetic field (T)

 0.45 K

 1.55 K

 1.82 K

 5.01 K
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2

0

2

4

6

8

10

7T Cp (J/mol-K)

T (K)

0T