Automated thermoelectric power measurement from 300 to 15 K with a closed cycle refrigerator
TL;DR: In this article, a compact sample holder to perform thermoelectric power measurements on small, bulk samples in the temperature range of 300-15 K is designed and attached to a closed cycle refrigerator.
Abstract: A compact sample holder to perform thermoelectric power measurements on small, bulk samples in the temperature range of 300–15 K is designed and attached to a closed cycle refrigerator (CCR). Differential method is employed and copper is taken as the reference material. The temperature control as well as the data acquisition are automated.
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TL;DR: A simple but precise thermoelectric power measurement setup that can be adapted for different environments and achieved good precision both in natural warm-up/cooldown and controlled measurements is reported.
Abstract: We report here on a simple but precise thermoelectric power measurement setup that can be adapted for different environments. This setup has been extensively used for cryogen-free environment to measure a variety of samples. It is made simple to load and hold the sample between two copper blocks by a spring-shaft arrangement. The usable range of measurements is a few microV/K to a few hundreds of microV/K. The salient features of the setup in achieving good precision both in natural warm-up/cooldown and controlled measurements are (i) the continuous DeltaT control across the sample by a chromel-AuFe(0.07%) thermocouple and (ii) the measurements of emf generated across the sample and the thermocouple using a nanovoltmeter and a scanner system. The versatile nature of the setup is further demonstrated by employing it in a magnetic field environment up to 140 kOe. The precision achieved using this system is highlighted for a few systems of current interest.
44 citations
TL;DR: In this article, the Griffiths temperature at which ferromagnetic metallic clusters nucleate above TC was evaluated and it was shown that Griffiths phase extends over a higher temperature range above TC with increase in the variance of ionic radii of the A site.
Abstract: We report our analysis of thermopower S(T) of Pr(0.7−x)HoxSr0.3MnO3 (x=0, 0.04, 0.08, and 0.1) compounds within a percolative framework and correlate the results with the existence of a Griffiths phase. The Griffiths temperature, at which ferromagnetic metallic clusters nucleate above TC, is evaluated. We further show that the Griffiths phase extends over a higher temperature range above TC with increase in the variance of ionic radii of the A site.
4 citations
TL;DR: In this article , an experimental setup has been designed and fabricated with a new configuration for measuring both thermopower as well as resistivity of different type of samples (bulk and thin film) in the temperature range 80-300 K.
Abstract: • Design and fabrication of Thermopower and electrical resistivity set up. • Continuous ΔT control is used in the differential method to measure thermopower of thin films and bulk samples in this setup. • Using continuous ΔT control we can record high density of data points with an accuracy and precision better than 0.5 μV/K. An experimental setup has been designed and fabricated with a new configuration for measuring both thermopower as well as resistivity of different type of samples (bulk and thin film) in the temperature range 80–300 K. The setup utilizes a differential method for measuring the thermopower of samples. The sample holder in the present setup has been designed in such a way that, samples of lengths ∼2.5–15 mm can be loaded easily with the help of spring–shaft arrangement. Electrical leads, as well as controlled ΔT by chromel-AuFe (0.07 %) thermocouple, are mounted on the copper blocks. Manganin wires of resistance 50 Ω are used as heating elements and wound on the copper blocks. Generated emf of the sample and the thermocouple are measured using nanovoltmeter. The present configuration allows simple way of applying temperature difference to bulk and thin film systems. The setup allows continuous ΔT control across the sample by chromel-AuFe (0.07 %) thermocouple to achieve accuracy and precision with the nanovoltmeter, scanner switching system and Visual Basics software programme used for automatic measurements. The measurements are carried on standard bulk samples Mn, Mo and Mo thin film. Results are well in agreement with reported values.
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TL;DR: The results of magnetic susceptibility, electrical resistivity and heat capacity measurements on the pseudoternary solid solutions, Pr1−xGdxCu2Si2, are reported in this article.
Abstract: The results of magnetic susceptibility, electrical resistivity and heat capacity measurements on the pseudoternary solid solutions, Pr1−xGdxCu2Si2, are reported. These is an unusual enhancement of Neel temperature (TN) of Pr sub-lattice in PrCu2Si2 (TN = 21K) over that of GdCu2Si2 (TN = 13K). Present results indicate that this anomalous magnetism gets relatively depressed by positive chemical pressure effects induced by Gd or Y substitution. Interestingly, the linear coefficient of heat capacity above TN is found to be large for PrCu 2 Si 2 (∾225 mJ/mol K 2 ) and this parameter undergoes a drastic reduction with Gd substitution. Such a strong dependence of this linear term on the positive chemical pressure indicates possible heavy fermion behaviour of Pr in a metallic environment.
19 citations
TL;DR: In this article, the results of electrical resistance, magnetic susceptibility and heat capacity measurements extended to low temperatures (well below 4.2 K) were reported, and it was shown that the existence of a discontineous phase transition is possible due to a change in the magnetic structure.
Abstract: The compound PrCu2Ge2 is known to order antiferromagnetically at about 16 K. In this article, we report the results of electrical resistance, magnetic susceptibility and heat capacity measurements extended to low temperatures (well below 4.2 K). The results establish the existence of a discontineous phase transition at 4.2 K, in addition to the 16K-antiferromagnetic transition, possibly due to a change in the magnetic structure. Metamagnetic isothermal magnetization behaviour at 2 K and 5 K is observed at about 15 KOe thereby suggesting strong anisotropic nature of the exchange interaction.
10 citations
01 Jul 1963
TL;DR: In this article, a modification of the electronic structure of α-manganese below the Neel temperature has been supplemented by thermoelectric and magnetoresistive data.
Abstract: Evidence from electrical resistivity studies of a modification of the electronic structure of α-manganese below the Neel temperature has been supplemented by thermoelectric and magnetoresistive data. The thermoelectric power changes from negative to positive on cooling through the Neel temperature (similar 95 °K). The magnetoresistance increases by a factor of 10 between 110 and 65 °K.
10 citations