In this work, we investigate the magnetic structures of $(Fe_{1-x}Mn_x)_2AlB_2$ solid-solution quaternaries in the $x = 0$ to $1$ range using x-ray and neutron diffraction, magnetization measurements, and mean-field theory calculations. While $Fe_2AlB_2$ and $Mn_2AlB_2$ are known to be ferromagnetic (FM) and antiferromagnetic (AFM), respectively, herein we focused on the magnetic structure of their solid solutions, which is not well understood. The FM ground state of $Fe_2AlB_2$ becomes a canted AFM at $x \approx 0.2$, with a monotonically diminishing FM component until $x \approx 0.5$. The FM transition temperature ($T_C$) decreases linearly with increasing $x$. These changes in magnetic moments and structures are reflected in anomalous expansions of the lattice parameters, indicating a magnetoelastic coupling. Lastly, the magnetocaloric properties of the solid solutions were explored. For $x = 0.2$ the isothermal entropy change is smaller by 30% than it is for $Fe_2AlB_2$, while the relative cooling power is larger by 6%, due to broadening of the temperature range of the transition.
Role of Fe substitution on the anomalous magnetocaloric and magnetoresistance behavior in Tb(Ni1-xFex)2 compounds
我们报告的磁性，磁热和磁电阻的结果在Tb（Ni 1-xFex）2化合物与x=0，0.025和0.05。Fe取代导致的有序温度从36 K x=0到124 K x=0.05的增加。与TbNi 2中看到的单个尖锐MCE峰相反，Fe取代的化合物的MCE峰相当宽。我们把这种反常的MCE行为归因于Fe取代引起的Tb矩的随机化。磁性和磁阻的结果似乎证实了这一命题。本研究还表明，在本化合物中观察到的异常磁热和磁电阻行为类似于Ho（Ni，Fe）2化合物。
A detailed study on the crystal structure and bulk magnetic properties of Cr substituted Ising type lanthanide gallium garnets $Ln_3\text{CrGa}_4\text{O}_{12}$ ($Ln$ = Tb, Dy, Ho) has been carried out using room temperature powder X-Ray and neutron diffraction, magnetic susceptibility, isothermal magnetisation and heat capacity measurements. The magnetocaloric effect (MCE) in $Ln_3\text{CrGa}_4\text{O}_{12}$ is compared to that of $Ln_3\text{Ga}_5\text{O}_{12}$. In lower magnetic fields attainable by a permanent magnet ($\leq$ 2 T), Cr substitution greatly enhances the MCE by 20% for $Ln$ = Dy…
Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB$_{2}$. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho$_{1-x}$Dy$_{x}$B$_{2}$ alloys ($\textit{x}$ = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature ($\textit{T}$$_{C}$) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |$Δ\textit{S}_{M}$| at $\textit{T}$ = $\textit{T}_{C}$ decreases from 0.35 to 0.15 J cm$^{-3}$ K$^{-1}$ for a field change of 5 T. Due to the pr…
We report the effect of partial substitution of Dy-site by rare-earths (R=Gd, Er and La)on the magnetic and magnetocaloric behavior of a mixed metal oxide DyFe0.5Cr0.5O3.Structural studies reveal that substitution of Dy by R has a minimal influence on the crystal structure. Magnetic and heat capacity studies show that the magnetic transition around 121 K observed for DyFe0.5Cr0.5O3 remains unchanged with rare-earth substitution, whereas the lower magnetic transition temperature is suppressed/enhanced by magnetic/non-magnetic substitution. In all these compounds, the second order nature of magn…
Influence of Ni substitution on the phase transitions and magnetocaloric effect of NdCo2 at cryogenic temperatures
Institute for Energy Technology (IFE)（能源技术研究所）；Technical University of Darmstadt（达姆施塔特工业大学）；Helmholtz-Zentrum Dresden-Rossendorf（亥姆霍兹德累斯顿-罗斯多夫中心）；Technische Universität Dresden（德累斯顿工业大学）；Paul Scherrer Institute (PSI)（保罗谢勒研究所）
Giant magnetocaloric (GMC) materials constitute a requirement for near room temperature magnetic refrigeration. (Fe,Mn)$_2$(P,Si) is a GMC compound with strong magnetoelastic coupling. The main hindrance towards application of this material is a comparably large temperature hysteresis, which can be reduced by metal site substitution with a nonmagnetic element. However, the (Fe,Mn)$_2$(P,Si) compound has two equally populated metal sites, the tetrahedrally coordinated $3f$ and the pyramidally coordinated $3g$ sites. The magnetic and magnetocaloric properties of such compounds are highly sensiti…
We investigate the magnetocaloric effect (MCE), relative cooling power (RCP) and crystalline structure in Sb substituted CrTe_{1-x}Sb_{x} (0 \leq x \leq 0.2) alloy. The Rietveld refinement of the XRD pattern of CrTe1-xSbx showed the emerging of pure hexagonal NiAs structure with P63/mmc (194) space group with increasing Sb substitution. We detect a slight increase in the basal plane a-lattice parameter, with a much larger reduction in the c-axis. Magnetic isotherms were measured in the temperature range of 50-400K. The results revealed an increase in the maximum entropy change |S_{M}(T,H)| wit…
The nature of the magnetic transition, critical scaling of magnetization, and magnetocaloric effect in Mn$_{1+x}$Fe$_{4-x}$Si$_{3}$ ($ x =$ 0 to 1) are studied in detail. Our measurements show no thermal hysteresis across the magnetic transition for the parent compound which is in contrast with the previous report and corroborate the second order nature of the transition. The magnetic transition could be tuned continuously with Mn substitution at the Fe site. The Mn substitution leads to a linear increase in the unit cell volume and a slight reduction in the effective moment. A detailed critic…
Cluster glass behavior and magnetocaloric effect in the hexagonal polymorph of disordered Ce$_2$PdGe$_3$
Gdansk University of Technology（格但斯克理工大学）；A. Chełkowski Institute of Physics, University of Silesia in Katowice（卡托维兹西里西亚大学A.切科夫斯基物理研究所）；Institute of Molecular Physics, Polish Academy of Sciences（波兰科学院分子物理研究所）
Using Density Functional Theory and a thermodynamic model [Physical Review B 86, 134418 (2012)], in this paper, we provide an approach to systematically screen compounds of a given Heusler family to predict ones that can yield giant magnetocaloric effect driven by a first-order magneto-structural transition. We apply this approach to two Heusler series Ni$_{2-x}$Fe$_{x}$Mn$_{1+z-y}$Cu$_{y}$Sb$_{1-z}$ and Ni$_{2-x}$Co$_{x}$Mn$_{1+z-y}$Cu$_{y}$Sb$_{1-z}$, obtained by cosubstitution at Ni and Mn sites. We predict four new compounds with potentials to achieve the target properties. Our computation…
We report a systematic investigation of the magnetic and magnetocaloric properties of Dy5Pd2 and Dy5PdNi. Our study on these compounds gave evidence that they exhibit complex magnetic behaviour along with the presence of glass-like magnetic phase. Furthermore, in these compounds both second order and first order phase transitions were present, which were validated through Arrott plots and Landau parameter analysis. AC susceptibility along with time dependent magnetisation study has confirmed the presence of double cluster glass-like freezing in both Dy5Pd2 and Dy5PdNi. These compounds show sig…
Derivation of a non-stoichiometric 1/1 quasicrystal approximant from a stoichiometric 2/1 quasicrystal approximant and maximization of magnetocaloric effect
In previous studies, we have reported that double perovskite La2NiMnO6 presents a non-negligible potential for room temperature magnetocaloric tasks. With the aim of improving even further the cooling performances and the working temperature range of double perovskites, we report the magnetic and magnetocaloric properties of La2MnFeO6 and ALaMnFeO6 (A = Sr, Ba, Ca) compounds. X-ray diffraction (XRD) and Rietveld refinement show that La2MnFeO6 (LMFO) and CaLaMnFeO6 (CLMFO) samples crystallize in an orthorhombic structure with the Pnma space group. However, a rhombohedral structure with the R3C …
Cementite-type carbides are of interest for magnetocaloric applications owing to their temperature- or pressure-induced magnetic phase transition. Here, using first-principles calculations, we investigate the magnetism and the magnetic phase transition in iron carbide (Fe3C) with the substitution of Cr atoms at Fe sites with the strain effect. The presence of Cr atoms is found to give rise to a second-order magnetic phase transition from a ferromagnetic phase for Fe3C to a nonmagnetic phase in chromium carbide (Cr3C).While the ternary Fe2CrC and Cr2FeC compounds prefer the ferrimagnetic ground…
We study the magnetocaloric effect and critical behavior of Co$_2$Cr$_{1-x}$Mn$_x$Al ($x=$ 0.25, 0.5, 0.75) Heusler alloys across the ferromagnetic (FM) transition (T$_{\rm C}$). The Rietveld refinement of x-ray diffraction patterns exhibit single phase cubic structure for all the samples. The temperature dependent magnetic susceptibility $χ$(T) data show a systematic enhancement in the Curie temperature and effective magnetic moment with Mn concentration, which is consistent with the Slater-Pauling behavior. The M(H) isotherms also exhibit the FM ordering and the analysis of $χ$(T) data indic…
Magnetostructural Transformation and Magnetoresponsive Properties of MnNiGe1-xSnx Alloys
采用X射线衍射（XRD）、差热分析（DTA）和磁化强度测量方法研究了MnNiGe 1-xSnx（0 \leq x \leq 0.200）合金的马氏体相变和磁相变。结果表明，随着Sn替代量的增加，MnNiGe_（1-x）Sn_x的马氏体相变温度从460 K降低到100 K，马氏体中AFM螺旋结构转变为反平行AFM结构。在此基础上，获得了显著的磁场诱导PM/spiral-AFM和FM/AFM磁结构转变以及较大的正、负磁热效应。Mn Ni Ge_（1-x）Sn_x合金的磁响应效应因Sn的替代而增强。提出了MnNiGe_（1-x）Snx合金的结构和磁性相图。
We present here the improved crystallographic/geometric compatibility and magnetocaloric reversibility by measurement of magnetic entropy change using different protocols in 10% Pt substituted Ni2Mn1.4In0.6 magnetic shape memory alloy. The substitution of Pt reduces the thermal hysteresis about 50% to the Ni2Mn1.4In0.6. The origin of the reduced thermal hysteresis is investigated by the crystallographic compatibility of the austenite and martensite phases. The calculated middle eigenvalue of the transformation matrix turned out to be 0.9982, which is very close to 1 (deviation is only 0.18%) s…
研究了MgB超导体$_2$中硼平面的碳替代效应。在高压炉中合成了MgB $_2$和MgB $_{1.8}$ C $_{0.2}$样品。MgB $_{1.8}$ C $_{0.2}$的特征是具有较小B-B距离的AlB $_2$型单相。在超导转变过程中，在MgB $_{1.8}$ C $_{0.2}$中观察到两个不同的起始温度。
We investigate the structural, magnetic and spin-state transitions, and magnetocaloric properties of Sr$_{2-x}$La$_x$CoNbO$_6$ ($x=$ 0--1) double perovskites. The structural transition from tetragonal to monoclinic phase at $x$ $\geqslant$ 0.6, and an evolution of (101)/(103) superlattice reflections and Raman active modes indicate the enhancement in the B-site ordering with $x$. The magnetic susceptibility data reveal the transition from weak ferromagnetic (FM) to antiferromagnetic (AFM) ordering for $x$ $\geqslant$ 0.6 with T$_{\rm N}$$\approx$9--15~K. Interestingly, the La substitution driv…
Polycrystalline La1-xPbxMnO3+-y (x = 0.3, 0.35, 0.4) solid solutions were prepared by solid state reaction method and their magnetic properties have been investigated. Rietveld refinement of X-ray powder diffraction patterns showed that all samples are single phase and crystallized with the rhombohedral structure in the R-3c space group. A second order paramagnetic to ferromagnetic phase transition was observed for all materials. The Griffiths phase (GP), identified from the temperature dependence of the inverse susceptibility, was suppressed by increasing magnetic field and showed a significa…
We report the effect of carbon doping in Ti-stabilized nonstoichiometric molybdenum diboride (Mo$_{0.96}$Ti$_{0.04}$)$_{0.8}$B$_{2}$, which exhibits bulk superconductivity below $T_{\rm c}$ = 7.0 K. It is found that (Mo$_{0.96}$Ti$_{0.04}$)$_{0.8}$(B$_{1-x}$C$_{x}$)$_{2}$ maintains the AlB$_{2}$-type phase with a uniform elemental distribution for $x$ = 0.12 and 0.16. The substitution of carbon for boron leads to a slight increase in $a$-axis, a remarkable reduction in $c$-axis, the formation of planar defects along the (100) crystallographic planes, and a shift of the B 1$s$ peaks towards hig…
The structural, magnetic, magnetocaloric and Griffiths phase (GP) disorder of non-stoichiometric perovskite manganites La_(0.8-x) Sr_(0.2-y) Mn_(1+x+y) O_3 are reported here. Determination of valence states and structural phases evidenced that the smaller cations Mn2+ and Mn3+ will not occupy the A-site of a perovskite under atmospheric synthesis conditions. The same analysis also supports that the vacancy in the A-site of a perovskite induces a similar vacancy in the B-site. The La3+ and Sr2+ cation substitutions in the A-site with vacancy influences the magnetic phase transition temperature …
We report the structural, magnetic, and magnetocaloric properties of Co$_2$Cr$_{1-x}$Ti$_x$Al ($x=$ 0--0.5) Heusler alloys for spintronic and magnetic refrigerator applications. Room temperature X-ray diffraction and neutron diffraction patterns along with Rietveld refinements confirm that the samples are of single phase and possess a cubic structure. Interestingly, magnetic susceptibly measurements indicate a second order phase transition from paramagnetic to ferromagnetic where the Curie temperature (T$_{\rm C}$) of Co$_2$CrAl increases from 330~K to 445~K with Ti substitution. Neutron powde…
