共查询到20条相似文献,搜索用时 93 毫秒
1.
J. Satooka A. Fukaya A. Ito E. Torikai K. Nishiyama K. Nagamine 《Hyperfine Interactions》1997,104(1-4):363-368
A cluster‐glass (CG) Fe0.25Mg0.75TiO3 is investigated by muon spin relaxation measurements. It is found that the local magnetic fields at the muon stopping site
are established at temperatures five times as high as the freezing temperature Tf. It is also found that the electron spins fluctuate even below Tf. The critical region around Tf in Fe0.25Mg0.75TiO3 is extremely wide in contrast to that of ordinary spin‐glass (SG) systems. It is clearly demonstrated that the microscopic
and dynamical properties of CG are remarkably different from those of SG.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
G.M. Kalvius T. Takabatake A. Kratzer R. Wäppling D.R. Noakes S.J. Flaschin F.J. Burghart R. Kadono I. Watanabe A. Brückl K. Neumaier K. Andres K. Kobayashi G. Nakamoto H. Fujii 《Hyperfine Interactions》1997,104(1-4):157-164
The temperature dependence of the muon spin relaxation rate \lambda was measured in two samples of CeNiSn with markedly different
impurity content and in the quasi‐ternary compounds CePtxNi1-xSn (x=0.12,\ ,0.2) and CeCuxNi1-xSn (x=0.05,\ ,0.1,\ ,0.2) in order to study the development of magnetic correlations. No significant change in \lambda was
found for the two samples of CeNiSn although their low temperature specific heat differs strongly. Hence μSR probes the intrinsic
magnetic properties of the spin‐liquid state of CeNiSn. Replacing Ni with up to 20% Pt results only in minor changes of \lambda.
In contrast, a strong effect is seen when Ni is replaced by Cu. Already at 10% Cu the system forms a spin‐glass‐like state
below 0.9 K. At 20% Cu this behavior is strengthened, but antiferromagnetic order of the type seen in CePtSn or CePdSn is
not reached. The results show further that the change in 4f hybridization initiated by volume expansion in the alloyed samples
is not the dominating mechanism strengthening the magnetic correlations. Decisive is the increase in d electron density when
replacing Ni by Cu.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Fukaya A. Satooka J. Ito A. Torikai E. Nishiyama K. Nagamine K. 《Hyperfine Interactions》1999,120(1-8):615-618
The diluted antiferromagnet MnxMg1-xTiO3 transforms from the antiferromagnet (AF) to the spin-glass (SG) system at x ∼ 0.6. In order to study the microscopic nature
of spin dynamics and ordering, we performed muon spin relaxation measurements for the powder samples of x=1.0∼ 0.55 and examined
the concentration dependence. From these results, a drastic change in the spin dynamics was found to occur at x ∼ 0.6.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
L. Cristofolini A. Lappas K. Prassides K. Vavekis M. Buchgeister 《Hyperfine Interactions》1997,104(1-4):61-66
The zero‐field μ+SR technique is employed to study the magnetic properties of the non‐superconducting borocarbides Sm1-xLuxNi2B2C (x=0.0,\ 0.2) and NdPt1.5Au0.6B2C. Coherent ordering of the Sm electronic moments appears below TN=9.86(3) and 4.15(3) K for the x=0.0 and 0.2 compositions, respectively. No long range order of the Nd3+ moments is found in NdPt1.5Au0.6B2C down to 80 mK. Freezing of the electronic moments into a spin‐glass state occurs at Tf\approx 1.2 K. A stretched exponential decay of the μ+ spin polarisation is observed above Tf with the exponent \beta smoothly decreasing on approaching Tf from above, reminiscent of the behaviour in other spin glasses.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Zero‐field μSR measurements have been carried out in the paramagnetic and magnetically ordered states of the heavy fermion
alloys: Ce1-xLaxRu2Si2 (x=0.05,0.13,0.25). In Ce1-xLaxRu2Si2 system, TK drastically decreases with x from 24 K for x=0 and becomes very close to the magnetic ordering temperature TN. As functions of TK and TN, the magnetic instabilities were studied in this system. For x=0.05,\ 0.13\ \mboxand\ 0.25 samples, longitudinal muon spin
relaxation was measured to study non‐magnetic to magnetic transition and the change from itinerant to localized electron state
with increasing La impurities. We discuss the dynamics of muon spins in the paramagnetic and antiferromagnetic state.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Magnetic interaction in Mg, Ti, Nb doped manganites 总被引:4,自引:0,他引:4
I.O. Troyanchuk M.V. Bushinsky H. Szymczak K. Bärner A. Maignan 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):75-80
An effect of Mn substitution with Me=Mg2+, Ti4+, Nb5+ in manganites has been investigated by preparing La0.7Sr0.3(Mn1-xMex)O3 and La1-xSrx(Mn1 - x/2Nbx/2)O3 series. It was established that substitution of manganese with magnesium up to x = 0.16 leads to a collapse of a long-range ferromagnetic order whereas La0.7Sr0.3(Mn 3 +
0.85Nb 5 +
0.15)O3 is ferromagnet with T
C = 123 K and exhibits a large magnetoresistance below Curie point despite an absence of four-valent manganese. Hypothetical
magnetic phase diagrams are constructed for La0.7Sr0.3(Mn1-xMex)O3 and La1-xSrx(Mn1 - x/2Nbx/2)O3. Our results show that Mn3+-O-Mn3+ exchange interaction is ferromagnetic in the orbitally disordered manganites as well as an increase of Mn4+ content above 50% from a total amount of manganese ions leads to formation of a spin glass state due to a competition between
antiferromagnetic Mn4+-O-Mn4+ and ferromagnetic Mn3+-O-Mn4+(Mn3+) superexchange interactions.
Received 24 January 2002 Published online 9 July 2002 相似文献
7.
Ch. Niedermayer C. Bernhard T. Blasius A. Decker A. Golnik 《Hyperfine Interactions》1997,105(1-4):131-137
We have studied the magnetic phase diagram for the bilayer compound Y1-x Cax Ba2 Cu3 O6 in the regime of low doping (hole concentration within a CuO2 plane, psh < 0.1). For psh < 0.03, the data demonstrate the freezing of the spin degrees of freedom associated with the doped holes into a spin‐glass‐like
state which is superimposed on the preexisting long range order of the Cu2+ spins. Only a single spin‐glass like transition at a temperature Tg is observed for samples in the hole concentration range 0.03 < psh < 0.1. While the threshold for the occurrence of superconductivity is almost the same (psh > 0.06) for the Y1-x Cax Ba2 Cu3 O6 and the La2-x Srx CuO4 systems, the magnetic correlations that coexist with superconductivity are considerably stronger in the bilayer Y1-x Cax Ba2 Cu3 O6 system as indicated by significantly increased transition temperatures Tg.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
The synthesis and characterization are reported for the cubic spinel titanate Mg(2−x)NixTiO4 (x≤0.25) and Mg(2−x)MnxTiO4 (x≤1). Single phase samples were observed for Mg(2−x)NixTiO4 and with x≤0.4 for Mg(2−x)MnxTiO4. AC measurements were carried out on four different compositions (x=0.01, 0.03, 0.04 and 0.15) in the Mg(2−x)NixTiO4 series and for Mg1.9Mn0.1TiO4. For all these compounds, increasing conductivity with temperature and Arrhenius conductivity dependence are observed, the
activation energy is around 0.28 eV for the Ni compounds and is 0.184 eV for Mg1.9Mn0.1TiO4. The DC conductivity was recorded over a range of oxygen partial pressures (10−19 to 1 atm) at 930 °C. The Mg(2−x)NixTiO4 compounds show a n-type behaviour whereas the Mg(2−x)MnxTiO4 show a p-type behaviour at high p(O2) and n-type at low p(O2). The stability under reduced conditions was checked and discussed for the different synthesized compounds.
Paper presented at the 5th Euroconference onSolid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
9.
Satooka J. Fukaya A. Ito A. Torikai E. Nishiyama K. Nagamine K. 《Hyperfine Interactions》1999,120(1-8):611-614
The diluted antiferromanget FexMg1-xTiO3 which transforms from the antiferro-magnetic (AF) system to the cluster-glass (CG) one with dilution is investigated by muon
spin relaxation measurements. We compare the concentration dependence of the spin dynamics of FexMg1-xTiO3 with that of FexMn1-xTiO3 and MnxMg1-xTiO3 which transform from the AF system to the spin-glass one depending on x. It is found that the shape and the temperature variation
of the time spectrum in FexMg1-xTiO3 for AF to CG depends on the Fe concentration most strongly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
Hidetoshi Fukuyama 《Hyperfine Interactions》1997,104(1-4):17-21
The spin‐gap phenomenon is a key characteristic of high Tc superconducting cuprates, whose experimental results are summarized and discussed in the context of the slave‐boson mean
field theory of the extended t–J model. It is seen that there exists satisfactory agreement between theory and experiments
in bilayer cuprates. As regards the apparent absence of the spin‐gap in single layer La2-xSrxCuO4 (LSCO), the possible roles played by disorder have been pointed out in view of the recent neutron scattering experiment on
other spin singlet systems, the spin‐Peierls CuGeO3 and two‐leg ladders.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
用超导量子干涉器(SQUID)磁强计对稀释磁性半导体Zn1-xMnxSe(0.1≤x≤0.50)的低温低场直流磁化率作了测量,测量温度从4.2K到30K,测量磁场为15Oe。当x≥0.30时,从磁化率-温度曲线的浑圆峰值,观察到了自旋玻璃的转变。自旋玻璃的转变温度Tf,对x=0.30,0.40,0.50,分别为10.5K,16K,19.5K。给出了顺磁相和自旋玻璃相的相图。比较了Zn1-xMnxSe和Cd1-xMnxSe的自旋玻璃转变温度,发现对同样的Mn离子浓度,Zn1-xMnxSe的Tf高于Cd1-xMnxSe的Tf,用交换作用的理论作了讨论。
关键词: 相似文献
12.
通过研究铁磁性金属间化合物Ni2+xMn1-xGa(x=-0.1,0,0.08,0.13,0.18,0.2)和Ni2-xMn1+x/2Ga1+x/2(x=-0.1,0,0.04,0.06,0.1)两个系列多晶样品的交流磁化率随温度的变化行为,得到了化合物在不同组分下的马氏体相变温度TM和居里温度TC.发现随着Ni成分的增加,前者的马氏体相变温度Tm增加,而居里温度TC降低,后者的马氏体相变温度Tm和居里温度TC均是先增大后减小.报道了Tm在室温附近的单晶样品Ni52Mn24Ga24的磁场增强双向形状记忆效应.发现伴随着马氏体相变,样品在[001]方向可产生1.2%的收缩.如果在该方向施加1.2T的偏磁场可以使该应变值增大到4.0%.而垂直于[001]方向施加1.2T的偏磁场时,在[001]方向产生1.6%的膨胀.阐明了产生大应变的原因并非相界移动,而是单晶的杂散内应力小和外加磁场通过孪晶界移动使马氏体变体重组的共同结果.
关键词:
形状记忆效应
马氏体相变
2MnGa')" href="#">Ni2MnGa 相似文献
13.
G.M. Luke K. Kojima M. Larkin J. Merrin B. Nachumi Y.J. Uemura Y. Nakamura S. Uchida M. Crawford 《Hyperfine Interactions》1997,105(1-4):113-117
We present μSR experiments on La2-x Bax CuO4 and La1.6-x Nd0.4 Srx CuO4 for x=0.125. Both of these materials order magnetically with TN\approx30\ K, while a superconducting sample of La1.4 Nd0.4 Sr0.2 CuO4 showed no evidence for static copper moments. Our results support the conclusion that the so‐called “1/8” anomaly in La2-x Bax CuO4 is a result of static (pinned) charge segregation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
L.P. Le R.H. Heffner D.E. Maclaughlin K. Kojima G.M. Luke B. Nachumi Y.J. Uemura J.L. Sarrao Z. Fisk 《Hyperfine Interactions》1997,104(1-4):91-96
Magnetic properties of the Li‐doped cuprates La2Cu1-xLixO4 (where x=0.01,\ 0.05,\ 0.10,\ 0.45, and 0.50) have been studied by μSR. For low Li concentrations (x\Eleq 0.10) we find a
rapid suppression of TN as x increases, but little change in the magnitude and temperature dependence of the AFM order parameter. This indicates
that Li doping effectively destroys AFM (similar to Sr doping, but different from Zn doping) without strongly affecting the
onsite Cu moments and the shape of the spinwave excitation spectrum. For high Li concentrations we find magnetic clusters
in about 15% of the sample volume; the remaining volume is non‐magnetic, suggesting possible singlet‐state formation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
K. Kojima A. Keren L.P. Le M. Larkin G.M. Luke B. Nachumi W.D. Wu Y.J. Uemura M. Azuma M. Takano K. Kiyono S. Miyasaka N. Motoyama H. Takagi S. Uchida M. Hase Y. Sasago K. Uchinokura M. Matsuda K. Katsumata A. Revcolevschi R. Cava 《Hyperfine Interactions》1997,104(1-4):37-42
We introduce our μSR investigations of spin‐gap systems, such as, (1) a 2‐leg spin‐ladder material SrCu2O3, (2) a Haldane material (S=1 spin‐chain) Y2BaNiO5, (3) a spin‐Peierls material CuGeO3, (4) a spin‐chain# material Sr6Ca8Cu24O41. All of these antiferromagnetic spin systems are characterized by a spin‐gap between the singlet ground‐state and the triplet
first excited states. In the above‐mentioned materials, we confirmed the absence of magnetic order down to milli‐Kelvin regime,
supporting the non‐magnetic feature of the ground‐state.
If a spin‐gap system is doped with charges and/or vacancies at the spin site, unpaired spins are induced out of the singlet
ground‐state. In some materials, doping completely destroys the singlet ground‐state and induces a bulk magnetic order. We
report μSR investigations of doped materials as well, which clarifies the existence/absence of a magnetic order upon doping.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Hiroshi Yasuoka 《Hyperfine Interactions》1997,105(1-4):27-34
From the temperature dependence of the 63Cu nuclear spin‐lattice relaxation rate, 1/T1T, in the planar Cu(2) sites, it is now well established that a highly enhanced and strongly temperature dependent relaxation
process due to antiferromagnetic Cu spin fluctuations exists in all of the high‐Tc’s. The data also exhibit the opening of a gap in the low‐lying magnetic excitations with an energy comparable to the superconducting
gap, particularly for the so‐called low doping regime. It is also found that, irrespective of the system, the temperature
at which the spin‐gap opens, Tsg, determined as the peak of 1/T1T vs. T, has a linear decrease with increasing of the doping concentration. A spin‐gap phase diagram is proposed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
The double-doped La2/3+4x/3Sr1/3-4x/3Mn1-xMgxO3 samples with fixed Mn^3+/Mn^4+ ratio equal to 2/1 are investigated by means of magnetism and transport measurements. Phase separation is observed at temperature higher than T^onset c for x = 0.10 and 0.15. For x = 0.10, rather strong phase separation induces drastic magnetic random potential and results in the localization of carriers. Thus, the varlable-range hopping process dominates. For other samples, there is no or only weak phase separation above T^onset c. Thus, thermal activation mechanism is responsible for the high temperature transport behaviour. For x = 0.20 and 0.25, unexpected AFM behaviour is observed at low temperature. All these results are well understood by considering the special role of the "double-doping". 相似文献
18.
Atsuko Ito Keiko Iwai Chiyuki Oyama Setsu Morimoto Hiroaki Kato 《Hyperfine Interactions》1992,71(1-4):1371-1374
Magnetization and Mössbauer measurements have been made on a diluted antiferromagnets FexMg1?xTiO3 with x=0.2, 0.3 and 0.7. It has been demonstrated that this system exhibits a spin glass or a reentrant spin glass like behavior in the samples with x around the percolation concenrration xc≈0.25. It has been shown that various sizes of magnetic clusters are formed well above the transition temperatures determined by the magnetization measurements in the samples with x near xc. The behavior of Fe0.2Mg0.8TiO3 is discussed as a typical cluster glass. 相似文献
19.
K.H. Chow Th. Jestädt S.J. Blundell S.R. Dunsiger W. Hayes B. Hitti M.A. Green R.F. Kiefl J.E. Millburn P.A. Pattenden F.L. Pratt M.J. Rosseinsky 《Hyperfine Interactions》1997,104(1-4):55-60
We report μSR measurements on a series of compounds with composition La2-xSrxNiO4+\delta where the net hole concentration x+2\delta is greater than 0.4. A magnetic transition is found in all the samples studied
which occurs at a composition‐dependent temperature TM. Below TM, clear precession signals are observed in zero applied magnetic field. The possible muon sites are discussed within the context
of dipole‐field calculations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
D. P. Belanger 《Phase Transitions》2013,86(1-4):53-89
Experiments in d = 2 and d = 3 random-field Ising systems are reviewed. Random fields destroy the phase transition for the d = 2 system Rb2Co x Mg1-xF4. The d = 3 Fe x Zn1-xF4 system shows a new phase transition with unusual dynamics. Extreme critical slowing down plays an essential role in the d = 3 measurements. Experiments on the related d = 3 systems Mn x Zn1-xF2 and Fe x Mg1-xC12 are also discussed. 相似文献