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1.
通过结构以及磁性测量,研究了哈斯勒合金Ni50Mn25+xSn25-x (x=11,12)的马氏体相变和磁热性质.结果表明,与样品在奥氏体相的磁性不同,由于在马氏体相中反铁磁交换作用的增强,导致铁磁和反铁磁在马氏体状态下共存.此外,通过Maxwell方程,研究了两样品在不同磁场变化下马氏体相变温度附近的反磁热性质,并阐明了该系列合金产生大的正磁熵变(ΔSM)不仅与其在降温过程中发生马氏体相变所导致的磁跃变(ΔM)有关,而且与发生马氏体相变所经历的温度区间有密切的联系.
关键词:
哈斯勒合金
Ni-Mn-Sn
马氏体相变
正磁熵变 相似文献
2.
Tb$lt;sub$gt;0.3$lt;/sub$gt;Dy$lt;sub$gt;0.6$lt;/sub$gt;Pr$lt;sub$gt;0.1$lt;/sub$gt;(Fe$lt;sub$gt;1-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;Al$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;)$lt;sub$gt;1.95$lt;/sub$gt;合金的磁性、磁致伸缩和穆斯堡尔谱研究 下载免费PDF全文
系统研究了室温下Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 (x=0.05,0.1,0.15,0.2,0.25,0.3)合金中元素Al替代Fe对结构、磁性、磁致伸缩性能和自旋重取向的影响.测量结果发现,x<0.2时Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金基本上是纯的单相,x=0.2时出现其他杂相,杂相随Al替代量的增加不断增多.随Al替代量x的增加,点阵常数a接近于线性增大,Curie温度TC逐渐下降,而矫顽力Hc急剧下降.振动样品磁强计(VSM)测量发现,磁化强度M随Al替代量x的变化较为复杂.VSM计和磁致伸缩效应测量共同表明,少量Al的替代有利于降低磁晶各向异性,而且随着Al替代量x的增多磁致伸缩系数快速减小,x>0.15时巨磁致伸缩效应消失.穆斯堡尔效应研究发现,随Al含量的增加Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金中易磁化轴可能在{110}面逐渐偏离了立方晶体的主对称轴,发生自旋重取向,从而引起合金宏观磁性、磁致伸缩性能的变化.
关键词:
磁致伸缩
立方Laves相
自旋重取向
穆斯堡尔谱 相似文献
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4.
对A位掺杂的La1-xSrxFeO3-δ氧化物体系进行了低频内耗测量.研究发现此体系的内耗和模量-温度谱随Sr掺杂量(x)的不同而变化.当Sr含量x=0时,LaFeO3-δ体系的内耗和模量在测量温度范围内(-150—380℃)没有明显变化;而当x=0.2,0.25,1/3以及0.5时,掺杂样品均观察到一个与正交—三角相变对应的相变型内耗峰P1,且其峰温随x增加向低温移动.在x=0.25,1/3,0.5,0.6以及2/3的样品中还观察到一个弛豫型特征的内耗峰P2,此峰伴随着模量的变化,可归于畴壁的运动.进一步分析表明畴壁是受氧空位钉轧的.在x=0.5,0.6以及2/3样品的模量-温度谱上呈现出的模量急剧变化是与三角—立方铁弹性相变有关的.
关键词:
内耗
畴壁
钉扎
铁弹性相变 相似文献
5.
采用金属有机物化学气相沉积(MOCVD)法在蓝宝石(0001)衬底上制备出了Ga2(1-x)In2xO3(x=01—09)薄膜,研究了薄膜的结构、电学和光学特性以及退火处理对薄膜性质的影响.测量结果表明:当In组分x=02时,样品为单斜β-Ga2O3结构;x=05的样品,薄膜呈现非晶结构,退火处理后薄膜结构得到明显的改善
关键词:
金属有机物化学气相沉积
2(1-x)In2xO3薄膜')" href="#">Ga2(1-x)In2xO3薄膜
蓝宝石衬底
退火 相似文献
6.
利用电弧炉制备了Ni50-xFexMn37In13(x=1, 3, 5) 多晶样品, 通过结构和磁性测量, 系统分析了Ni50-xFexMn37In13(x=1, 3, 5)样品的晶体结构和马氏体相变. 结果表明, 三样品在室温下呈现出了不同的晶体结构. 同时, 随着Fe含量的增加, 样品的马氏体相变温度急剧下降, 而铁磁性却逐渐增强. 研究了Fe3和Fe5样品在反马氏体相变过程中的磁电阻和磁卡效应. 在外加3 T的磁场下, 两样品在反马氏体相变区域所表现出的磁电阻效应分别约为-46%和-15%, 而等温熵变则约为6 J·kg-1·K-1和9.5 J·kg-1·K-1. 然而, 伴随非常宽的相变温跨和较小的磁滞损失, Fe3样品在反马氏体相变区域的净制冷量达到96 J·kg-1. 相似文献
7.
采用电弧熔炼法在高纯氩气保护下合成了一系列TbGa1-xGex(0≤x≤0.4)样品. X射线粉末衍射数据表明,样品均为正交晶系的CrB型结构,空间群为Cmcm. TbGa1-xGex化合物的晶格常数随Ge含量的增加而线性减小,TbGa和TbGe赝二元系在0≤x≤0.4范围内形成固溶体. 化合物的顺磁居里温度以及有效磁矩由热磁测量结果确定. 相变温度由交流磁化率的测量获得. 随Ge含量的增加,化合物的相变温度单调下降. 变温X射线粉末衍射实验表明,x=0.2和0.3的样品在110—273K范围内无结构相变.
关键词:
TbGa-TbGe 赝二元系
CrB结构
居里温度
磁化强度 相似文献
8.
针对NiS2-xSex系统在x=1.00附近发生的反铁磁量子相变,制备了一系列NiS2-xSex(x=0.96, 0.98, 1.00, 1.05, 1.10和1.20)多晶样品,对其结构、磁性质和电阻率进行了系统的观测.结果发现:样品磁化率-温度关系呈现典型的强关联电子系统特征;与铜氧化物超导体相类似,它们的电阻率-温度关系在很宽的温
关键词:
量子相变
反铁磁自旋涨落
2-xSex体系')" href="#">NiS2-xSex体系 相似文献
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通过对La2-xNdxCuO4+δ(0.1≤x≤1.2)体系中滞弹性弛豫与相变内耗性能的研究发现,当0.1≤x≤1.0时,在250K左右存在一个与间隙氧有关的弛豫内耗峰,并且当0.1≤x≤0.4时,弛豫内耗峰峰高随着x值的增大而升高,此时体系为正交结构;当0.5≤x≤1.0时,体系在宏观上呈现四方结构,此时内耗峰峰高随着x<
关键词:
2-xNd<i>xCuO4+δ')" href="#">La2-xNd<i>xCuO4+δ
间隙氧
弛豫内耗峰
相变内耗峰 相似文献
11.
Influence of Ni/Mn ratio on magnetostructural transformation and magnetocaloric effect in Ni_(48-x)Co_2Mn_(38+x)Sn_(12)(x = 0, 1.0, 1.5, 2.0,and 2.5) ferromagnetic shape memory alloys 下载免费PDF全文
An investigation on the magnetostructural transformation and magnetocaloric properties of Ni_(48-x)Co_2Mn_(38+x)Sn_(12)(x = 0, 1.0, 1.5, 2.0, and 2.5) ferromagnetic shape memory alloys is carried out. With the partial replacement of Ni by Mn in the Ni_(48)Co_2Mn_(38)Sn_(12) alloy, the electron concentration decreases. As a result, the martensitic transformation temperature is decreased into the temperature window between the Curie-temperatures of austenite and martensite. Thus, the samples with x = 1.5 and 2.0 exhibit the magnetostructural transformation between the weak-magnetization martensite and ferromagnetic austenite at room temperature. The structural transformation can be induced not only by the temperature,but also by the magnetic field. Accompanied by the magnetic-field-induced magnetostructural transformation, a considerable magnetocaloric effect is observed. With the increase of x, the maximum entropy change decreases, but the effective magnetic cooling capacity increases. 相似文献
12.
Effect of Sb-doping on martensitic transformation and magnetocaloric effect in Mn-rich Mn_(50)Ni_(40)Sn_(10-x)Sb_x(x=1,2,3,and 4) alloys 下载免费PDF全文
We investigate the influence of Sb-doping on the martensitic transformation and magnetocaloric effect in Mn_(50)Ni_(40)Sn_(10-x)Sb_x(x = 1, 2, 3, and 4) alloys. All the prepared samples exhibit a B2-type structure with the space group F m3 m at room temperature. The substitution of Sb increases the valence electron concentration and decreases the unit cell volume. As a result, the magnetostructural transformation shifts rapidly towards higher temperatures as x increases.The changes in magnetic entropy under different magnetic field variations are explored around this transformation. The isothermal magnetization curves exhibit typical metamagnetic behavior, indicating that the magnetostructural transformation can be induced by a magnetic field. The tunable martensitic transformation and magnetic entropy changes suggest that Mn_(50)Ni_(40)Sn_(10-x)Sb_x alloys are attractive candidates for applications in solid-state refrigeration. 相似文献
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We report on the magnetic properties and magnetocaloric effects of Mn_5Ge_{3-x}Ga_x compounds with x=0.1, 0.2, 0.3, 0.4, 0.6 and 0.9. All samples crystallize in the hexagonal Mn_5Si_3-type structure with space group P6_3/mcm and order ferromagnetically. The Curie temperature of these compounds decreases with increasing x, from 306K (x=0.1) to 274K (x=0.9). The average Mn magnetic moments increases with increasing Ga content, reaching a maximum value at x=0.6. The magnetic entropy changes in these compounds are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation. The Ga substitution has two kinds of influence on the magnetocaloric effect (MCE) of Mn_5Ge_3. One is that the magnitude of the magnetic entropy change decreases, the other is that the MCE peak becomes broadened. 相似文献
14.
Magnetoresistance and exchange bias in high Mn content melt-spun Mn_(46)Ni_(42)Sn_(11)Sb_1 alloy ribbon 下载免费PDF全文
Highly textured Heusler alloy Mn_(46)Ni_(42)Sn_(11)Sb_1 ribbons were prepared by melt spinning. The annealed high Mn content Mn46Ni42Sn11Sb1 ribbon cross-section microstructure, crystal structure, martensitic transformation(MT), and magnetoresistance(MR) properties were investigated. The MR in the annealed ribbon was assessed by the magnetic field direction perpendicular to the ribbon surface with the magnetic field up to 30 k Oe. The large negative value of 25% for MR was obtained at 244 K. The exchange bias(EB) effects of the as-spun and annealed ribbons were investigated. After annealing, the EB effects have been improved by about 25 Oe at the temperature of 50 K. The magnetizations have increased approximately by 10% more than the as-spun ribbon. 相似文献
15.
Effect of Ni substitution on the formability and magnetic properties of Gd_(50)Co_(50) amorphous alloy 下载免费PDF全文
《中国物理 B》2020,(5)
A small amount of Ni was added into the binary Gd_(50)Co_(50) amorphous alloy to replace Gd in order to obtain ternary Co_(50)Gd_(50-x)Ni_x(x = 1, 2, and 3) amorphous alloys. Compared to the binary Gd_(50)Co_(50) amorphous alloy, the Co_(50)Gd_(50-x)Ni_x amorphous alloys show an enhanced Curie temperature(T_C) with a weakened formability. The maximum magnetic entropy change(-?S_m~(peak)) of the Co_(50)Gd_(50-x)Ni_x amorphous alloys is found to decrease with the increasing T_C.The adiabatic temperature rise(?T_(ad)) of the Co_(50)Gd_(47)Ni_3 amorphous alloy is superior to that of the Fe-based metallic glasses at room temperature. The variation of the T_C and -?S_~(peak) of the Gd_(50)Co_(50) amorphous alloy with Ni addition, and the mechanism involved, were discussed. 相似文献
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Magnetic transitions and magnetoresistance effect of the HfFe_6Ge_6-type Y_{0.9}La_{0.1}Mn_6Sn_6 compound have been investigated in the temperature range of 5-380K. The sample displays antiferromagnetic behaviour in the whole temperature range below Néel temperature T_N=309K. The metamagnetic transition from antiferromagnetism to ferromagnetism can be induced by an applied field. The metamagnetic transition field decreases monotonically from 2T at 5K to 0.4T at 300K. The giant magnetoresistance effect is observed with the metamagnetic behaviour, such as -10.4% at 245K under a field of 5T. 相似文献
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Magnetic properties and magnetocaloric effect of the Cr-based spinel sulfides Co_(1-x)Cu_xCr_2S_4 下载免费PDF全文
Crystallographic structure, magnetic properties, and magnetic entropy change of the Cr-based spinel sulfides Co_(1-x)Cu_xCr_2S_4(x = 0–0.8) have been investigated. All these compounds crystallize into the cubic spinel structure, the Cu substitution shrinks linearly the lattice constant at a ratio of 0.0223 per Cu atom in the unit cell, and enhances linearly the Curie temperature and the spontaneous magnetization at the rates of 18K and 0.33 μB/f.u. per Cu atom in the unit cell,respectively. All these compounds show a typical behavior of second order magnetic transition, and a room temperature magnetic entropy change of 2.57 J/kg·K is achieved for Co_(0.4)Cu_(0.6)Cr_2S_4. 相似文献
20.
Magnetotransport properties and magnetocaloric effects of Mn1.95Cr0.05Sb0.95Ga0.05 compound 下载免费PDF全文
The magnetotransport properties and magnetocaloric effects of the compound Mn_{1.95}Cr_{0.05}Sb_{0.95}Ga_{0.05} have been studied. With decreasing temperature, a spontaneous first-order magnetic phase transition from ferrimagnetic (FI) to antiferromagnetic (AF) state takes place at T_s=200K. A metamagnetic transition from the AF to FI state can be induced by an external field, accompanied by a giant magnetoresistance effect of 57%. The magnetic entropy changes are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation. Mn_{1.95}Cr_{0.05}Sb_{0.95}Ga_{0.05} exhibits a negative magnetocaloric effect, and the absolute values of ΔS_M^{max}(T,ΔH) are 4.4, 4.1, 3.6, 2.8 and 1.5 J/(kg·K) for magnetic field changes of 0-5T, 0-4T, 0-3T, 0-2T and 0-1T, respectively. 相似文献