MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

Electronic and Magnetic Measurements 27
Silver paint contacts can be made quite small if the suspension has the
appropriate viscosity. These contacts can be used to low temperatures but are
often unreliable. I have had better results with the two component silver
epoxy (epo-tek ¨ 417).
Polyimide based silver epoxy (epo-tek ¨ P1011) can be used well above its
recommended maximum temperature of 300°C. It requires only a low
temperature curing and works almost up to the melting point of silver. This
was used for measurements to 1200K. A platinum paste is available for high
temperature contacts that requires a high temperature sintering.
3.1.2.4 Reproducibility
It is obviously important to only report reproducible data. Important data
should always be reproduced and claims about general properties of a
material should be reproduced on other samples or even types of samples. It
is best to simply not collect irreproducible data. If there is anything unusual
in the above checks, it is probably not worth the time collecting the data.
Extensive automation of the data collection system may actually help
increase the consistency of the measurement. If the temperature is changed
in a uniform way, the data tends to be more consistent than if points were
taken at random temperatures. This is probably due to temperature gradients
in the sample or sample chamber, that depend on the heating or cooling rate.
Measurements as a function of temperature should generally be measured
while heating and cooling in case there is some temperature differential
between the sample and the thermometer. Some contacts break easily when
rapidly cooled, requiring the slow cooling of an automated system. With
enough automation so that the experiment can be left unattended for several
hours or days, extra data can be collected. This allows more frequent checks
for linearity and reproducibility.