共查询到19条相似文献,搜索用时 156 毫秒
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借助与示差扫描量热法、磁化率测量、电子自旋共振、铁电与介电性质测量及电子衍射系统地研究了Pb(Fe1/2Nb1/2)O3(PFN)的电、磁性质和相变特征.结果表明发生在380K附近的顺电-铁电转变和发生在145K附近的顺磁 反铁磁转变分别为一级相变和二级相变或弱一级相变.在室温下,PFN的剩余极化与矫顽场分别为11.5μC/cm2和3.04kV/cm.介电测量表明PFN的顺电-铁电相变为弥散型相变.其弥散指数为1.62.电子衍射表明Fe3+与Nb5+离子在B位置上是无序分布的,正是这种与无序分布相关联的成分涨落导致铁电相变的弥散性.
关键词: 相似文献
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研究了Gd1-xCaxBa2Cu3O7-y(0.0≤X≤0.20)高温超导体在常压和高压下的超导电性在1-300K温度范围内,利用Bridgman对顶砧获得压力达9.0GPa,测量了(X=0.10,0.15,0.20)样品的dTc/dp分别为7.68,7.8和4.46K/GPa。发现Tc的压力导数随着ca2+含量的增加而下降,分析了氧含量对Tc和dTc/dP的影响.利用常压下晶格参数精修值和阳离子与氧离子间距随压力的改变,说明CuO2面在超导电性上的作用,用CuO2面之间耦合解释Tc(P)曲线的非线性关系。
关键词: 相似文献
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利用电弧炉熔炼了Ni50Mn35In15多晶样品,根据磁性测量对其马氏体相变和磁热效应进行了系统研究.结果表明,随着温度的降低,样品在室温附近先后发生了二级磁相变与一级结构相变特征的马氏体相变,导致它的磁化强度产生突变. 同时通过低温下的磁滞回线的测量发现样品存在交换偏置行为,表明低温下马氏体相中铁磁和反铁磁共存. 此外,根据Maxwell方程,计算了样品在马氏体相变温度附近的磁熵变,当温度为309K,磁场改变5 T时,样品的磁熵变可达22.3J/kgK.
关键词:
哈斯勒合金
50Mn35In15')" href="#">Ni50Mn35In15
马氏体相变
磁热效应 相似文献
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测量了Ni52Mn24Ga24单晶样品在磁场加载和未加载情 况下马氏体相变时的相变应变.分析结果表明:用提拉法生长单晶时在晶体内部引入了单一取向的内应力,该取向内应力可诱导马氏体变体择优取向,从而导致马氏体相变时产生大的相变应变.从理论上计算了该内应力的大小.另外,对样品在马氏体态单纯磁诱导应变的热动力学研究,表明取向内应力在马氏体态依然存在.
关键词:
马氏体相变
磁感生应变
内应力 相似文献
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在活塞圆筒式P~V关系测量装置上,研究了KH_2PO_4(KDP)和(CH_3NHCH_2CO-OH)_3CaCI_2[Tris-sarcosinecalciumchloride(TSCC)]在室温下、4.5GPa内的p~V关系。实验结果表明:KDP在2.1GPa左右有一个相变;TSCC在0.8GPa和3.2GPa左右各有一个相变。本工作还给出了它们在相变前后的状态方程,以及它们的格临爱森参数γO、体积模量B_o和B_o的压力导数B_o。 相似文献
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D. Starešinić D. Dominko K. Salamon K. Biljaković A. Tomeljak H. Schäfer T. Huber J. Demsar G. Socol C. Ristoscu I.N. Mihailescu Z. Siketić I. Bogdanović Radović G. Pletikapić V. Svetličić M. Đekić H. Šamić J. Marcus 《Physica B: Condensed Matter》2012,407(11):1889-1893
Thin granular films of charge density wave (CDW) system K0.3MoO3 were prepared by pulsed laser deposition and investigated by various standard characterization methods such as GI-XRD, electric transport, TOF-ERDA, AFM and UV–visible spectroscopy. While all these methods indicate that the thin films consist of nanometer grains of K0.3MoO3, it is only the non-destructive femtosecond time-resolved spectroscopy (fsTRS) that demonstrates the charge density wave nature of the ground state and therefore proves directly the presence of K0.3MoO3. Furthermore, the comparison of the fsTRS data obtained in thin films and in single crystals shows the reduction of the charge density wave transition temperature and of the photoinduced signal strength in granular thin films with respect to single crystals, which is attributed to the granularity and crystal growth morphology. Our results establish fsTRS technique as the essential tool for the detection and characterization of complex ground states in nano-sized systems. 相似文献
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The optical reflectivity of the blue bronze K0.3MoO3 has been measured on single crystals for photon energies between 0.03 and 12 eV at temperatures from 10 to 300 K using polarized light. The data are interpreted that this compound is a one-dimensional conductor for temperatures above 180 K and that the metal-semiconductor transition at 180 K is due to a Peierls type transition, leading to a gap of 0.15 eV in the density of states. 相似文献
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M. Greenblatt W.H. McCarroll R. Neifeld M. Croft J.V. Waszczak 《Solid State Communications》1984,51(9):671-674
Four probe electrical resistivity measurements between 0.3K and 300K were made on single crystals of the violet-red bronze Li0.9Mo6O17 grown by a temperature gradient flux technique. The temperature variation of the resistivity shows metallic conductivity and highly anisotropic behavior similar to K0.9Mo6O17. The room temperature resistivity, measured in the direction parallel to the plate axis, is 9.5×10-3Ωcm and 2.47Ωcm perpendicular to that axis. A phase transition observed at ~24K is possibly related to the onset of a charge density wave. A transition to the superconducting state is observed at Tc ~ 1.9K. 相似文献
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B.T. Collins K.V. Ramanujachary M. Greenblatt J.V. Waszczak 《Solid State Communications》1985,56(12):1023-1028
Single crystals of Tl0.3MoO3 blue bronze were grown by the temperature gradient flux technique for the first time. Tl0.3MoO3 crystalizes with monoclinic symmetry, space group C2, C2/m or Cm, , , , β = 118.377(6)° and appears to be isostructural with the K0.3MoO3 blue bronze. The physical properties of Tl0.3MoO3 are similar to those of the K3MoO3 and Rb3MoO3 phases. The resistivity of Tl0.3MoO3 is highly anisotropic and its temperature susceptibility (4.2–300K) decreases sharply with decreasing temperature near the transition seen in the resistivity. The onset of another transition <60K is also indicated by the susceptibility data. Non-linear current-voltage (I–V) characteristics observed at ~70K above applied threshold voltages of the order of ~300mV/cm suggest the sliding of charge density condensate. 相似文献
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Junfeng Wang Di Yin Zhengyou Liu Decheng Tian Yuheng Zhang 《Solid State Communications》2004,132(10):653-656
The thermoelectric power (TEP) of the quasi-one-dimensional charge-density-wave (CDW) conductors rubidium blue bronze Rb0.3MoO3 and its alloy Rb0.15K0.15MoO3 were measured in the temperature range 80-280 K. The result showed a sign change from a small positive value to a great negative value where the Peierls transition temperatures (Tp) are 183 and 180 K for Rb0.3MoO3 and Rb0.15K0.15MoO3, respectively. Above Tp, the TEP for both samples can be described with the empirical relation S=AT+B; while below Tp, the TEP fits well the relation S=AT+B/T based on the experimental data. The Fermi energies εF for Rb0.3MoO3 and Rb0.15K0.15MoO3 are estimated to be 1.55 and 0.53 eV, respectively. 相似文献
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G. Remenyi 《Physics letters. A》2009,373(46):4278-4281
The charge density wave (CDW) dynamics of the quasi-one-dimensional conductor K0.30MoO3 shows two different regimes depending on the temperature: a strongly damped CDW motion above ∼50 K and CDW motion with almost no damping below ∼50 K. In a search for a characterization of this CDW behaviour, we performed thermal expansion measurements on K0.30MoO3 single crystals in the temperature range 4-250 K. In addition to the anomaly observed at the Peierls transition at 180 K along the [102] direction, an anomaly is observed at ∼50 K along the [−201] and [102] directions. The results are discussed in relation with the change in the CDW rigidity at ∼50 K. 相似文献
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Junfeng Wang Rui Xiong Changzhen Li Di Yin Zheng Tang Ququan Wang Jing Shi Xiaokui Qin 《Solid State Communications》2006,139(7):323-327
The specific heat of the quasi-one-dimensional charge-density-wave (CDW) compound Tl0.3MoO3 has been measured using an adiabatic continuous heating method from 100 to 220 K. A specific heat jump associated with the Peierls phase transition occurs at 172.3 K. A good scaling relation between the excess specific heat and the susceptibility is found between 140 K and 190 K. Further analysis indicates that the width of the critical region of Tl0.3MoO3 is about 10 K and the specific-heat critical behavior can be well described by the three-dimensional XY model. 相似文献
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The Raman spectra of an oriented single crystal of Rb2ZnBr4 shows three soft modes. One of them is interpreted as the amplitude mode of the incommensurate phase. The second one, seen well below the lock-in transition temperature appears as the phase mode. Moreover, an additional soft mode is observed between T=120 K and T=20 K, in the b(c, c)a scattering geometry. By extrapolation it is found that its frequency would vanish around T3=140 K ± 10 K. This soft mode is likely to be related to a new phase transition. 相似文献