(d) Co7

Zn7Mn6

Zn Mn

Zn

Mn

 Co8

Zn9Mn3

5

9

13

17

21

25

0 1 2 3 4 5 6

0

1

2

3

4

20

15

10

5

0

0

nSLD solvent 2, ρn

2

 (10-6 Å-2)

nSLD solvent 1, 

ρ

n

1 (10

Information gain, 

Δ

4 8 12 16 20 24

Counting time, t (h)

ADVANCES IN MEASUREMENT

2019 ACCOMPLISHMENTS AND OPPORTUNITIES 49

In-situ sample orientation at 

cryogenic temperatures

S. Gladchenko1

1 NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899

T

he nature of magnetism changes both with temperature 

and applied magnetic field. Typically, for elastic and inelastic 

scattering on single crystals the magnetic field should be 

precisely aligned along either the spin direction, or one of the 

crystallographic axes of the crystal. Unfortunately, with our standard 

vertical field magnets the sample environment equipment does 

not allow the scientist to control the crystal alignment. Rather, 

the crystal would be aligned separately and then inserted in the 

magnet. Subsequent alignment of the scattering plane requires 

tilting the entire assembly and does not allow any realignment of 

the sample with respect to the magnetic field direction. To address 

this issue, we have developed a system that allows realigning the 

sample inside the cryostat, changing its orientation relative to the 

magnetic field during a neutron experiment without disrupting 

the experiment temperature and magnetic field conditions.

Design of such a system is a challenging problem due to the 

limitations for devices operated at ultra-low temperatures. The 

alignment device must be located inside the small space under 

vacuum conditions, it should produce minimal heat load to 

avoid interference with stable operation of the refrigerator, and 

it should demonstrate minimal expansion or contraction over a 

wide range of temperatures. Additionally, the device must not 

generate an electromagnetic field and must be made from nonmagnetic materials. Previous designs have had both positives 

and negatives. Some designs used a worm-gear mechanism 

to mechanically connect an external room temperature motor 

to the sample space [1]. Another design used a piezoelectric 

actuator located at ultralow temperatures to achieve sample 

rotation [2]. However, these actuator systems were not designed 

for neutron measurements. Our current design for sample rotation 

allows 360° rotation around the axis in the horizontal plane with 

resolution 0.1°. The device can be used at temperatures below 

1 K, magnetic fields up to 31 T, under high vacuum, and within a 

neutron beam. Figure 1 is a photo of the actual device.

Dimensions of this device are 98 mm high and 55 mm wide which 

allows it to fit inside the 3He cryostat inserts operated within our 

facility. The dimensions are mostly defined by the size of the piezo 

electric rotator ANR240 (closed loop) by Attocube. The choice 

of this rotator was motivated by the amount of dynamic torque 

supplied (2 N·cm) to allow repositioning and maintaining sample 

position in a high magnetic field. An aluminum sample holder 

is attached to the bottom gear located at the neutron beam 

position. The piezo electric rotator and gears are supported by a 

ceramic (AlOx) frame. Figure 1 shows how the device has been 

designed to minimize the amount of material surrounding the 

sample position. The 0.6 in wide horizontal opening creates a 

large viewing window for undisturbed 360° sample observation. 

We use aluminum or copper braids to connect the sample holder 

and cold plate to improve thermal contact down to the 3He insert 

base temperature (T = 0.3 K).

This sample alignment device has been successfully used 

in exploring the metamagnetic transition in the intrinsic 

antiferromagnetic topological insulator MnBi2Te4. Tilting the 

sample at high field and low temperature allowed researchers 

to access otherwise inaccessible reflections sensitive to changes 

in the magnetic ordering while maintaining a large component 

of the magnetic field along the c-axis. This alignment device is 

a powerful tool for researchers, allowing them to more easily 

search for novel relationships between scattering geometry and 

applied magnetic field direction. 

References

[1] E.C. Palm, T.P. Murphy, Review of Scientific Instruments 

70(1), 237 (1999).

[2] L.A. Yeoh, A. Srinvasan, T.P. Martin, O. Klochan, A.P. 

Micolich, A.R. Hamilton, Review of Scientific Instruments 

81, 113905 (2010).

FIGURE 1: Low-temperature goniometer.