Structural and transport properties of some UTX compounds where T = Fe, Co, Ni and X = Si, Ge

Canepa, F.; Manfrinetti, P.; Pani, M.; Palenzona, A.

doi:10.1016/0925-8388(95)02037-3

Cited by 93 publications

(78 citation statements)

References 12 publications

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“…The compounds URhGe and UCoGe both crystallize in the orthorhombic TiNiSi structure (space group P nma ) [9,10]. The Curie temperatures are 9.5 K [11] and 3.0 K [2], respectively, and superconductivity is found below 0.25 K [1] and 0.8 K [2], respectively.…”

Section: Introductionmentioning

confidence: 99%

Ferromagnetic order in U(Rh, Co)Ge

Huy

Visser

2009

Solid State Communications

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Abstract:We report the variation of ferromagnetic order in the pseudo-ternary compounds URh 1-x Co x Ge (0 ≤ x ≤ 1). Magnetization and transport data taken on polycrystalline samples show that the Curie temperature T C gradually increases with increasing Co content from a value of 9.5 K for URhGe to a maximum value of 20 K for x = 0.6 and then steadily decreases to 3 K for UCoGe. The magnetic interaction strength varies smoothly across the series. For all samples the electrical resistivity for T < T C follows the behaviour ρ = ρ 0 + AT 2 . The A coefficient is dominated by scattering at spin waves and is strongly enhanced for x = 0 and 1.

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Section: Introductionmentioning

confidence: 99%

Ferromagnetic order in U(Rh, Co)Ge

Huy

Visser

2009

Solid State Communications

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“…UCoGe crystallizes in the orthorhombic TiNiSi structure (space group P nma ) [10,11], just like URhGe. From magnetization, resistivity (T 4:2 K) [9,10] and specific-heat measurements (T 1:2 K) [12] it was concluded that UCoGe has a paramagnetic ground state.…”

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confidence: 99%

Superconductivity on the Border of Weak Itinerant Ferromagnetism in UCoGe

et al. 2007

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We report the coexistence of ferromagnetic order and superconductivity in UCoGe at ambient pressure. Magnetization measurements show that UCoGe is a weak ferromagnet with a Curie temperature T C 3 K and a small ordered moment m 0 0:03 B . Superconductivity is observed with a resistive transition temperature T s 0:8 K for the best sample. Thermal-expansion and specific-heat measurements provide solid evidence for bulk magnetism and superconductivity. The proximity to a ferromagnetic instability, the defect sensitivity of T s , and the absence of Pauli limiting, suggest triplet superconductivity mediated by critical ferromagnetic fluctuations. DOI: 10.1103/PhysRevLett.99.067006 PACS numbers: 74.70.Tx, 74.20.Mn, 75.30.Kz In the standard theory for superconductivity (SC) due to Bardeen, Schrieffer, and Cooper ferromagnetic (FM) order impedes the pairing of electrons in singlet states [1]. It has been argued, however, that on the border line of ferromagnetism, critical magnetic fluctuations could mediate SC by pairing the electrons in triplet states [2]. The discovery several years ago of SC in the metallic ferromagnets UGe 2 (at high pressure) [3], URhGe [4], and possibly UIr (at high pressure) [5], has put this idea on firm footing. However, later work provided evidence for a more intricate scenario in which SC in UGe 2 and URhGe is driven by a magnetic transition between two polarized phases [6 -8] rather than by critical fluctuations associated with the zero temperature transition from a paramagnetic to a FM phase. Here we report a novel ambient-pressure FM superconductor UCoGe. Since SC occurs right on the border line of FM order, UCoGe may present the first example of SC stimulated by critical fluctuations associated with a FM quantum critical point (QCP).UCoGe belongs to the family of intermetallic UTX compounds, with T a transition metal and X is Si or Ge, that was first manufactured by Troć and Tran [9]. UCoGe crystallizes in the orthorhombic TiNiSi structure (space group P nma ) [10,11], just like URhGe. From magnetization, resistivity (T 4:2 K) [9,10] and specific-heat measurements (T 1:2 K) [12] it was concluded that UCoGe has a paramagnetic ground state. This provided the motivation to alloy URhGe (Curie temperature T C 9:5 K) with Co in a search for a FM QCP in the series URh 1ÿx Co x Ge (x 0:9) [13]. Magnetization data showed that T C upon doping first increases, has a broad maximum near x 0:6 (T max C 20 K) and then rapidly drops to 8 K for x 0:9 [13]. This hinted at a FM QCP for x & 1:0. In this Letter we show that the end (x 1:0) compound UCoGe is in fact a weak itinerant ferromagnet. Moreover, metallic ferromagnetism coexists with SC below 0.8 K at ambient pressure.Polycrystalline UCoGe samples were prepared with nominal compositions U 1:02 CoGe (sample 2) and U 1:02 Co 1:02 Ge (sample 3) by arc melting the constituents (natural U 99.9%, Co 99.9%, and Ge 99.999%) under a high-purity argon atmosphere in a water-cooled copper crucible. The as-cast samples were annealed for 10 days at 850 C. Sampl...

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“…Bulk and neutron-diffraction studies on UNiGe indicated two antiferromagnetic transitions at about 42 and 50 K [31][32][33][34][35][36][37][38]. High-field magnetization measurements [34] showed that there are two metamagnetic transitions in UNiGe for field applied along c axis (at 3 and lOT) and two transitions with field along the b-axis (at 17 and 25 T).…”

Section: Unigementioning

confidence: 99%

Radio-frequency measurements of UNiX compounds (X=Al, Ga, Ge) in high magnetic fields

Alsmadi¹,

Alyones²,

Mielke³

et al. 2009

Journal of Magnetism and Magnetic Materials

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We performed Radio-Frequency (RF) skin-depth measurements of anti ferromagnetic UNiX compounds (X = AI, Ga, Ge) in an applied magnetic fields up to 60 T in the temperature range from 1.4 up to about 60 K. Magnetic fields are applied along different crystallographic directions and RF penetration-depth measurements were done using a tunnel diode oscillator (TDO). The TDO couples the sample to the inductive element of a resonant tank circuit, and the shift in the resonant frequency ilf of the circuit is measured. The UNiX compounds exhibit (sometimes multiple) field-induced magnetic transitions in applied magnetic fields at low temperatures, and those transitions are accompanied by a drastic change in ilf. The results of our skin-depth measurements were compared with previously published B-T phase diagrams for these three compounds.

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Structural and transport properties of some UTX compounds where T = Fe, Co, Ni and X = Si, Ge

Cited by 93 publications

References 12 publications

Ferromagnetic order in U(Rh, Co)Ge

Ferromagnetic order in U(Rh, Co)Ge

Superconductivity on the Border of Weak Itinerant Ferromagnetism in UCoGe

Radio-frequency measurements of UNiX compounds (X=Al, Ga, Ge) in high magnetic fields

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