Naikun SUN
金属学报(英文版)
The compound MnAs0.9P0.1 exhibits a multistep magnetic order-order transition from a helimagnetic γ-phase with Hα-type magnetic order to a ferromagnetic β-phase at 80 K and then to a helimagnetic α-phase at 203 K. The γ-β transition exhibits the characteristics of a first-order transition with a thermal hysteresis as large as 6 K, while the β-α transition is of second order with a thermal hysteresis smaller than 2 K and without magnetic hysteresis. With these two successive helimagnetism-related transitions, magnetic-entropy changes of -2.1 J/(kg•K) at 203~K for a field change from 0 to 5 T and 0.1 J/(kg•K) at 83 K for a field change from 0 to 1 T are obtained. Investigation of the magnetocaloric effect associated with a transition from Hα-type magnetic order to FM order may open a new route to explore candidates for magnetic refrigeration.
关键词:
Magnetocaloric effect
Li'an Han Changle Chen
材料科学技术（英）
Magnetocaloric and colossal magnetoresistance effects of the layered perovskite La1:4Sr1:6Mn2O7 compound have been studied. A broad peak of magnetic entropy change (-ΔSM) is found above the Curie temperature (TC=120 K), which can be associated with the existence of two-dimensional short range ferromagnetic order. Additionally, the curvilinear shape of -ΔSM for layered perovskite is quite different from that of the Ln1-xAxMnO3 probably arising from magnetocrystalline anisotropy. At the same time, a wide peak of colossal magnetoresitance effect near TC is found in the layered provskite La1:4Sr1:6Mn2O7.
关键词:
Magnetocaloric effect
Wei WU
,
Zai FENG
材料科学技术（英）
A systematic (Gd1-xREx)5Si4 (RE=Dy, Ho) alloys are investigated to estimate their magnetocaloric effect. The Curie points of (Gd1-x REx)Si4 alloys can tunable from 266 K to 336 K when RE=Dy, Ho; x=0~0.35 and 0~0.15, respectively, and decrease nearly linearly with increasing x. These alloys keep orthorhombic structures Ge5Sm4 and exhibit second order transition when they experience in a change magnetic field at about Curie points. The weight and voluminal magnetic entropy changes are about 3.5 J/(kg•K) and 23~29 mJ/(cm3•K) when magnetic field changes 0~2 T. The adiabatic temperatures changes (▽Tad) of these alloys at Curie points are larger than 1 K in a field change 0~1.4 T, the curve of ▽Tad is wide as that of Gd. The relative cooling power is about 0.8~0.9 J/cm3 when field changes 0~2 T, 55% of that of Gd. Comparing with Gd5(Si1-xGex)4, these alloys do not contain expensive element Ge, so that their cost are lower than the former. Because they could work at temperature region 260~340 K due to their Curie points can be tuned, which is an advantage comparing with Gd, these alloys are potential magnetic refrigerants working in a magnetic refrigerator with a low magnetic field at room temperatures.
关键词:
Magnetocaloric effect
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null
,
null
Yongli WU
,
O.Tegus
,
Weiguang ZHANG
,
S.Yiriyoltu
,
B. Mend Songlin
金属学报(英文版)
doi:10.1016/S1006-7191(08)60114-3
The magnetic properties and magnetocaloric effect in Fe4MnSi3Bx compounds with x=0, 0.05, 0.10, 0.15, 0.20, 0.25 have been investigated. X-ray diffraction study shows that all these compounds investigated crystallize in the Mn5Si3-type structure with space group P63/mcm. Boron insertion in the host ternary silicide Fe4MnSi3 does not change the crystal symmetry, only leads to an increase of the lattice parameters, indicating the B atoms entered the interstitial sites. With increasing B content, the Curie temperature shifts to higher temperatures. The maximal magnetic-entropy changes of the Fe4MnSi3Bx compounds with x=0, 0.10 and 0.20 are about 1.8 J/(kg·K), 1.8~J/(kg·K) and 1.6~J/(kg·K), respectively, for a field change from 0 to 1.5 T.
关键词:
Transition metal interstitial compounds
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null
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null
金林虎
,
姜炳植
低温物理学报
利用固相反应法制备了用Sr部分替换GdMnO3中Gd的锰基钙钛矿氧化物Gd0.7Sr0.3MnO3.X射线衍射表明其晶体结构为正交晶系,空间群为Pnma.通过测量样品在零场冷却和加场冷却下的磁化强度及磁化率随温度的变化曲线,得出样品显示亚铁磁特性,Mn和Gd两个子晶格相互反平行.根据居里-外斯定律得知其居里温度为61 K,Mn原子轨道磁矩对总磁矩贡献大约为1.04μB.最大外加磁场为7000 Oe时负磁熵变从-0.26 J/Kg K连续变化到0.22 J/Kg K,在37 K附近磁熵变近似等于零.
关键词:
钙钛矿锰氧化物
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亚铁磁性
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磁热效应
