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We present a sensitive heat capacity measurement method for use at temperatures between 300 and 700 K using a home-made calorimeter incorporating a Si–N membrane microcalorimeter and a commercial tube furnace. We employ a scanning relaxation method with the two relaxation times, in which temperature is scanned with a maximum speed up to ∼30 K/min to measure the heat capacity of sub-mg single crystals. The heat capacity of the addenda composed of the Si–N membrane and thermal grease is measured to be as small as ∼30 μJ/K. For the high temperature thermal grease, several materials such as In, Wood's metal, and silicone oil have been tested. We demonstrate the successful performance of this method with different scanning speeds by measuring the specific heat of Cu up to 620 K. A brief summary of advantages/disadvantages of this method vis-a-vis commercially available differential scanning calorimeters (DSCs) is given.

We report the effect of lateral designs and resultant parasitic thermal conductance on the absolute accuracy of microcalorimeters based on a silicon-nitride membrane. Thermal properties are quantified by the curve fitting scheme based on the thermal relaxation method with two thermal decay times. In the studies of various microcalorimeter layouts, the temperature dependence of errors in the absolute values of heat capacity was found to be approximately proportional to that of the thermal conductance between the isothermal platform and the temperature reservoir. Decreasing parasitic thermal conductance by modifying the lateral designs for the thermometer and heater allowed for absolute accuracies that were typically less than 5% in a temperature range between 20 and 300 K.

We report the specific heat measurement of a YCrO3 single crystal in a wide temperature range from 30 to 360 K by use of a newly designed microcalorimeter with high sensitivity about ∼1J/K. The measured heat capacity data exhibit a -like shape at the N´ eel temperature TN ≈ 140 K as consistent with the second order magnetic transition. When the phonon specific heat is subtracted by use of that of a non-magnetic analogue LaGaO3 with an orthorhombic structure, the remaining entropy is much higher than the expected magnetic entropy from Cr 3+ (S = 3/2) ions. We attribute the excess entropy to the additional phonon entropy caused by the monoclinic structure of YCrO3, which can be intimately related to its ferroelectric property. © 2006 Elsevier B.V. All rights reserved.

In the core of quantum Hall effect, intrinsic anomalous Hall effect (AHE), and intrinsic spin Hall effect lies the Berry phase, a quantum mechanical phase associated with an adiabatic change of the system. However, experimental evidences supporting this new recognition are scarce in three-dimensional systems. We report here that the anomalous Hall conductivity of metallic GaMnAs samples, when properly scaled by the carrier concentration, remains constant regardless of the ferromagnetic transition temperature from 50 to 160 K. In addition, the constant agrees with the theoretical prediction quite well. These qualitative and quantitative agreements support the idea of intrinsic AHE originated from momentum-space Berry phase firmly. Furthermore, the tunability of intrinsic AHE in the diluted magnetic semiconductors can be utilized in the semiconductor spintronics applications.

Investigating the scaling behavior of annealed ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ anomalous Hall coefficients, we note a universal crossover regime where the scaling behavior changes from quadratic to linear. Furthermore, measured anomalous Hall conductivities in the quadratic regime when properly scaled by carrier concentration remain constant, spanning nearly a decade in conductivity as well as over 100 K in ${T}_{C}$ and comparing favorably to theoretically predicated values for the intrinsic origins of the anomalous Hall effect. Both qualitative and quantitative agreements strongly point to the validity of new equations of motion including the Berry phase contributions as well as the tunability of the anomalous Hall effect.