scholarly journals Beating Thermal Deterioration of Magnetization with Mn4C and Exchange Bias in Mn–C Nanoparticles

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1056 ◽  
Author(s):  
Ping-Zhan Si ◽  
Xin-You Wang ◽  
Hong-Liang Ge ◽  
Hui-Dong Qian ◽  
Jihoon Park ◽  
...  
Keyword(s):  
Temperature Coefficient ◽  
Exchange Bias ◽  
Arc Discharge ◽  
Magnetic Ordering ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Thermal Deterioration ◽  
Increasing Temperature ◽  
P Type ◽  
Discharge Method

The magnetization of most materials decreases with increasing temperature due to thermal deterioration of magnetic ordering. Here, we show that Mn4C phase can compensate the magnetization loss due to thermal agitation. The Mn–C nanoparticles containing ferrimagnetic Mn4C and other Mn–C/Mn-O phases were prepared by using the traditional arc-discharge method. A positive temperature coefficient of magnetization (~0.0026 Am2 kg−1 K−1) and an exchange bias up to 0.05 T were observed in the samples. We ascribe the exchange bias to the co-existence of ferrimagnetic Mn4C/Mn3O4 and antiferromagnetic α-Mn(C)/MnO phases. The positive temperature coefficient of magnetization of the samples was ascribed to the presence of Mn4C phase, which is considered as a Néel’s P-type ferrimagnet.

The Temperature Dependent Breakdown Voltage For 4H- and 6H-SiC Diodes

2000 ◽  
Vol 622 ◽  
Author(s):  
Y. S. Lee ◽  
M. K. Han ◽  
Y. I. Choi
Keyword(s):  
High Temperature ◽  
Temperature Coefficient ◽  
Breakdown Voltage ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Ionization Coefficient ◽  
Temperature Dependent ◽  
Increasing Temperature ◽  
Temperature Applications

ABSTRACTThe breakdown voltages of 6H- and 4H-SiC rectifiers as function of temperature were modeled analytically in both non-reachthrough diode and reachthrough diode. The breakdown voltage was derived by the ionization integral employing accurate hole impact ionization coefficient. The breakdown voltage of SiC rectifiers was increased with increasing temperature and the positive temperature coefficient of breakdown voltage indicates that SiC rectifiers are suitable for high temperature applications. The breakdown voltages of both 6H- and 4H-SiC diodes were increased by M(T)-1/4 in NRDs and M(T)-1/8 in RDs.

Positive Temperature Coefficient of Resistance in MOCVD (Ba0.75Sr0.25)Ti1+yO3+z Films

2002 ◽  
Vol 748 ◽  
Author(s):  
S. Saha ◽  
D. Y. Kaufman ◽  
S. K. Streiffer ◽  
R. A. Erck ◽  
O. Auciello
Keyword(s):  
Temperature Coefficient ◽  
Weak Field ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Temperature Coefficient Of Resistance ◽  
Current Voltage ◽  
Ptcr Effect ◽  
Bst Films ◽  
Current Voltage Characteristics ◽  
Increasing Temperature

ABSTRACTThe leakage and dielectric properties of a thickness series (90–480 nm) of {100} fiber-textured MOCVD (Ba0.75Sr0.25)Ti1+yO3+z (BST) thin films on Pt/SiO2/Si were investigated. The temperature and voltage dependence of the permittivity were consistent with previous observations, where thinner films demonstrated a suppressed temperature and electric field response that transitioned to a more bulk-like response with increasing film thickness. The current-voltage characteristics showed two distinct regimes. At low fields the current displayed weak field dependence and a monotonic increase with increasing temperature. In contrast, positive temperature coefficient of resistance (PTCR) was observed in the high-field leakage current behavior. The PTCR behavior was more pronounced for thicker BST films. Factors contributing to the observed PTCR effect are outlined and contrasted with the description for bulk BaTiO3 ceramics.

Temperature Dependence of Hole Impact Ionization Coefficient in 4H-SiC Photodiodes

2009 ◽  
Vol 615-617 ◽  
pp. 311-314 ◽  
Author(s):  
W.S. Loh ◽  
J.P.R. David ◽  
B.K. Ng ◽  
Stanislav I. Soloviev ◽  
Peter M. Sandvik ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Different Temperatures ◽  
Ionization Coefficients ◽  
Increasing Temperature ◽  
The Impact ◽  
Good Agreement ◽  
Ionization Rates

Hole initiated multiplication characteristics of 4H-SiC Separate Absorption and Multiplication Avalanche Photodiodes (SAM-APDs) with a n- multiplication layer of 2.7 µm were obtained using 325nm excitation at temperatures ranging from 300 to 450K. The breakdown voltages increased by 200mV/K over the investigated temperature range, which indicates a positive temperature coefficient. Local ionization coefficients, including the extracted temperature dependencies, were derived in the form of the Chynoweth expression and were used to predict the hole multiplication characteristics at different temperatures. Good agreement was obtained between the measured and the modeled multiplication using these ionization coefficients. The impact ionization coefficients decreased with increasing temperature, corresponding to an increase in breakdown voltage. This result agrees well with the multiplication characteristics and can be attributed to phonon scattering enhanced carrier cooling which has suppressed the ionization process at high temperatures. Hence, a much higher electric field is required to achieve the same ionization rates.

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