CIF MPMS Procedures: Magnetic Property Measurement System...recommended for removing the sample rod...

Research SOP: Magnetic Property Measurement System

Central Instrument Facility, Department of Chemistry

© 2018 Colorado State University Proprietary and Confidential of 8

CIF MPMS Procedures:

Magnetic Property Measurement System

Control Authority Central Instrument Facility, Department of Chemistry, Colorado

State University

Title Magnetic Property Measurement System – Research SOP

Last Updated 25 April 2018

Author(s) Erin Stuckert

Contributors Brian Newell

Instrument Manager(s) Brian Newell (Materials Analysis Lab Manager –

[email protected], 1-6209)

mailto:[email protected]




I. Introduction

Additional resources can be found at http://cif.colostate.edu/materials-analysis/.

II. Safety Information

a. Personal Protective Equipment

i. Eye Protection must always be worn in the Central Instrument Facility(CIF).

ii. Hand Protection, specifically gloves appropriate for low temperature are

recommended for removing the sample rod from the MPMS chamber.

b. Burn Hazards

i. Due to the low temperatures of the MPMS chamber, the sample rod can be quite

cold and burn exposed skin.

c. Training

i. Unauthorized operation of the MPMS instrument is strictly prohibited. All users

must be trained by approved personnel within the protocols of the Central

Instrument Facility prior to operation of the instrument.

ii. This document alone does not serve as training, or a replacement in lieu of

training.

III. Operational Procedures

IMPORTANT NOTES:

• Before using the instrument:

o Check that the instrument’s He levels are within usable levels. If liquid helium level

becomes too low, the superconducting magnet may quench. To prevent this from

happening, the liquid helium should be maintained above the top of the magnet. This

corresponds to a liquid helium level of approximately 50%. If the helium level drops

below the top of the magnet, the field used should be limited.

▪ 40-50% He maximum field should be limited to 10,000 gauss

▪ 30-40% He maximum field should be limited to 1,000 gauss

▪ Below 30% He the magnet should not be charged with a magnetic field

o If the He levels are not within usable range please wait until the CIF has filled the He

to usable levels again or contact Brian Newell to request a fill as soon as possible.

o Check that the pump outside of the MPMS housing is functioning by placing your

hand near the fan on the pump. If you can’t feel air movement from the fan and the

pump appears to not be functioning please contact Brian Newell.

• Be sure to copy all of your data to another location for your records as the CIF

cannot guarantee all data will be backed up.

• Fill out the required information on the log sheet by the MPMS computer.

o Be sure to record the initial and final He levels and include any comments about your

type of analysis or problems that arise with the system.

a. Instrument Start-Up

i. Take the instrument out of Standby mode by clicking OK. (When not in

use the MPMS should always be in standby mode to minimize He waste

from the 44 L He dewer in the instrument.)

http://cif.colostate.edu/materials-analysis/




b. Energize the field and set temperature

i. Using the bar on the bottom of the window,

1. double click on Target field and in the Magnetic Field window,

change set field to 1000 Oersted (Oe)

2. double click on System and in the Temperature Parameters

window, under control change set point to 100 K. (If sample is

paramagnetic will likely go above 100 K and if diamagnetic will

likely go below 100 K. Your sample needs to have some

paramagnetic character for centering the sample.)




c. Preparing your sample for the instrument:

i. Sample mass should be 50-100 mg. (Need greater mass if looking at high

MW samples to get more free electrons/molecule.)

ii. Use a polycarbonate (usually) straw with PEG capsules, gelatin or PE bags

to contain sample. (*all samples should be in containment for ease of

retrieval should the sample fall into the chamber*)

iii. Bend straw in half,

1. use push pin to create 4 holes evenly spaced just below the halfway

point, insert sample into straw, then create 4 more holes evenly

spaced just above the sample. These holes help keep the sample

contained in the straw.

2. alternatively, you can use a scissors to cut an ~1mm section of the

straw and push it into the center of the straw creating a ledge for

your sample, insert your sample, then use the push pin to create 4

holes evenly spaced just above the sample.

iv. Get the sample rod, being careful of the Au/Au coated junction as it is

delicate and can be easily

damaged.

1. DC rod typically

used, use carbon fiber rod for less thermal expansion.

v. Insert the straw onto the end of the sample rod into the ferrule. Gently

twist the straw to secure it to the rod. Lower the blue cap to meet the

ferrule

d. To insert the sample rod into the instrument: (See Figure d below)

i. On the instrument, barely push down CW on the black lever to activate the

sensor to vent, and push the lever back up (orange venting light should

flash).

ii. Be sure one of the white dots on the blue cap on the rod is facing you and

the other is directed to the left. Watch that the rod does not hit the ceiling

and the straw does not pop off of the rod while slowly inserting the rod

straight down into the instrument until the straw is fully observed in the

viewing window and the blue cap sits in place of the plug. Close the black

side tabs to ‘lock’ the blue cap in place, and press black button to purge

airlock once, then once again after Ready lights up green.

iii. When instrument Ready for second time, push the black lever clockwise to

be vertical and in the open position. Slowly push the rod carefully near the

end going into the system, allowing the rod to go in as straight as possible.

(be careful of the joint between the two different metals, if the rod




catches on this joint or near the rod/straw joint, carefully twist the

rod as you push) Be sure the black bar on top of the rod is flush with the

instrument (twist the rod so the black plate fits under the loosened black

beads. Tighten the black beads to hold the rod in place.

e. Centering sample:

*The field should be 1000 Oe or 0.1 T before centering. Depending on your

experiment needs you may want to center your sample under conditions similar to

your experiment settings.

i. Click the center tab, then DC.

1. A window should pop up. Select initialize transport, then full DC

scan. (The full range the instrument can scan

through is 12 cm before taking any

measurements.) Click view to see a graph

showing you the centering progress. The

sample should be centered at 2 ± 0.02 cm

6b.

6c.

6a.




2. Always start with Full DC Scan (i.e. auto center) first. If the

sample won’t center or if sample loses magnetism, you will need to

Adjust Position (i.e. manual center).

a. Try to Auto Adjust first using 0.5 to 1 cm increments to

approach 2 ± 0.02 cm. *Larger increments are likely to

cause the adjustment to fail.

b. If the adjustment needed is several cm or Auto Adjust

continues to fail, use Manual Adjust and follow the

instructions in the pop up windows.

c. Loosen the metal ferrule on top of rod, click Ok, then

slightly (barely a few mm) pull up or push down on the rod,

finger tighten the ferrule, then click ok again. The

instrument will redo a 4 cm short center scan to check the

new center. *You may need to repeat the Manual Adjust

process or a combination of Manual Adjust and Auto

Adjust.

ii. Sample head options and their centering

3. DC transport sample head option

a. Scans 32 pts across the entire position range

then goes back through the scan a second time

from the beginning.

4. Reciprocating (RSO) sample head option

a. Scans 1000 points in a smaller position range

then extrapolates the rest of the curve.

b. This is a faster scan for most typical

experiments with less sample.

c. If T < ~130-150 K, can’t use the RSO because

the sample chamber is exposed.

f. Creating and running a sequence for data collection

i. Click Sequence tab, new to create

new sequence for data collection.

1. Add Sequence Commands

from the right sidebar by

double clicking on a

command. (These will be

dependent upon your

individual needs.)

scan

Position (cm)

2

Res

po

nse

(en

u)

Position (cm)

2

Res

po

nse

(en

u)

scan




*All sequences should include the following*

a. Under Sequence Commands>Measure, add set datafile to

create a folder where data are saved. You may add remarks

to describe the sequence in the sequence window.

i. This folder should be created under C drive in the

QdMPMS >Data folder.

b. Next, add Start Data Logging to your sequence before the

experiment starts (i.e. before set magnetic field) (this allows

us to monitor data collection and parameters to help

diagnose any potential issues that may arise).

i. In the Log Data window that opens, under Standard

Items tab, Select All.

ii. Under the General tab, choose Browse and give

your log file a name specifying log and save it in

your Data folder.

c. Add in the steps you desire to change/measure

temperature/field etc. (see below for more information)

d. Add steps Set temp 4.2 K, temp stable, and set magnetic

field 0 to your sequence to put the instrument into Standby

mode upon completion of your data collection. This will

conserve He until you can put the system in Standy mode in

person or using Team Viewer (click Instrument>Standby).

e. End your sequence with Stop Data Logging.

Things you may include in a sequence

f. You can add in pre-experiment steps to your sequence,

such as exposing the sample to a field or starting at a

specific temperature.

g. You can set sampling rate (specifically with Pd standard).

i. Longitudinal or translational squid




h. Set magnetic field to value desired (e.g. 50,000 Oe or 5 T)

i. Select oscillate from the dropdown menu (this is

quickest to set).

ii. If you don’t want to overshoot a particular signal

select no overshoot (this is a slower process)

iii. If select hysteresis, ramps the field positive then

negative alternatively so there is no remnant

magnetic field

i. Always want to have in high resolution mode.

j. Select a DC measurement will have a 4 cm scan length of

24 data pts, with 2 scans per measurement. You shouldn’t

have to change any other settings.

ii. To save a sequence select file save as and be sure to save the file under C

drive in the QdMPMS >Sequence folder.

iii. Click the play/start (top toolbar) or Run (left sidebar) button to start the

sequence data collection when ready.

iv. At any time during a measurement you can observe the sequence

status/step being executed by looking at the Sequence Status bar on the left

sidebar or by clicking Sequence tab>Status.

g. Team Viewer

i. You can look into your data collection and operate the instrument

remotely using Team Viewer. This allows you to check your data

collection during long data collection periods. (To use team viewer you

will need to record the ID and Password provided on the desktop. Keep in

mind if the computer is restarted, the password will be reset.)

h. Removing the sample rod and starting Instrument Standby

i. Remove the sample rod from the instrument by first loosening the black

beads, twist the black bar to disengage from the beads, and pull the rod up

until the straw is fully in the viewing window.

ii. Move the black knob back CCW to close.

iii. Flip the black tabs to ‘unlock’ the blue cap, pull the sample rod completely

out of the instrument and replace the blue plug, flip the black tabs to ‘lock’

the plug.

iv. Push the black Purge button once.

v. If the instrument is not already in Standby, click Instrument>Standby.

vi. Record your final He

consumption,

Instrument time and

any remaining pieces

of the log sheet before

leaving.

CIF MPMS Procedures: Magnetic Property Measurement System...recommended for removing the sample rod...

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