A top-loading sample chamber tube, radiation shield and the vacuum shroud for interfacing a closed-cycle helium refrigerator for use with a vibrating sample magnetometer have been designed and fabricated. A lowest temperature of 12 K is achieved at the sample. The eddy current effects in the copper sample chamber tube are minimized by the use of an electrically insulating epoxy resin medium. The sample temperature is measured by a GaAlAs diode sensor attached on a sensor mount which is inserted into the sample zone and kept in helium atmosphere. The vibrations of the cryocooler's cold head are isolated from the vibrating sample magnetometer's head by incorporating a bellows. Using this facility the magnetic transitions of some rare earth elements have been measured and compared with the literature data. © 1998 IOP Publishing Ltd.

G. Markandeyulu

Department Of Physics

V R Shah

K. V.S. Rama Rao

CLOSED-CYCLE HELIUM REFRIGERATOR

Vibrating sample magnetometer

CLOSED CYCLE MACHINERY

Copper

Eddy currents

ELECTRIC INSULATING MATERIALS

Epoxy resins

Helium

Magnetization

Magnetometers

Semiconducting Gallium Arsenide

Semiconductor diodes

Sensors

Refrigerators

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Interfacing of a closed-cycle helium refrigerator to a vibrating sample magnetometer for low-temperature (12-300 K) magnetization studies

Measurement Science and Technology

The results of low temperature magnetization measurements carried out on the Dy0.73Tb0.27Fe2-xCox system and their hydrogenated compounds are presented. Low temperature (12 K) magnetization data reveals a large increase in anisotropy in the hydrogenated compounds, attributed to a modification in crystalline electric field effects as a result of the orientational ordering of hydrogen atoms in the lattice. The discrete step-wise increase in magnetization upto a field of 2 kOe in the parent alloys and the hydrogenated compounds is attributed to spin-flip metamagnetism. © 1998 Elsevier Science Ltd. All rights reserved.

Solid State Communications

Spin-flip metamagnetism in the laves phase compounds Dy0.73Tb0.27Fe2-xCoxHn

Review of Scientific Instruments

Erratum: Linear thermal expansivity (1.5–300 K) and heat capacity (1.2–90 K) of Stycast 2850FT [Rev. Sci. Instrum. 68, 1312 (1997)]

A closed-cycle helium refrigerator is utilized for the development of a facility for performing Mossbauer and electrical resistivity studies at low temperatures down to 18 K. This facility includes a vibration isolation assembly in order to isolate the sample holder from the vibrations arising from the cold head of the closed-cycle refrigerator. A top-loading chamber and a set of bellows are used for this purpose. The performance of the system was tested by recording the spectra of natural iron foil at 300 K when the closed-cycle refrigerator was on and when it was off. The typical width of the outer lines of the Fe spectra obtained was 0.26 mm s-1, which indicates the effective isolation of vibration. A facility for electrical resistivity measurements by a four-probe method was also developed for use in the same facility for Mossbauer studies.

Low-temperature facility for Mossbauer and electrical resistivity studies using a closed-cycle helium refrigerator

Journal	Measurement Science and Technology
Publisher	Institute of Physics Publishing
ISSN	09570233
Open Access	No