Spin-flop transition and magnetic phase diagram in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>CaCo</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>revealed by torque measurements

Zhang, W.; Nadeem, K.; Xiao, Hao; Yang, Rui; Xu, Bing; Yang, Hao; Qiu, Xianggang

doi:10.1103/physrevb.92.144416

Cited by 29 publications

(27 citation statements)

References 40 publications

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“…Electronic structure calculations are consistent with the itinerant A-type AFM ground state and the small ordered moment [29]. Spin-flop transitions in single crystals of CaCo 2−y As 2 with the magnetic field H applied parallel to the c axis occur at H SF ∼ 3.5-3.7 T [25,26,30,31]. On the other hand, metallic SrCo 2 As 2 exhibits no magnetic transitions versus T [32].…”

supporting

confidence: 57%

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2
Sangeetha¹,
Smetana²,
Mudring³
et al. 2017
Phys. Rev. Lett.
21
3
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0
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The inference of Ying et al. [EPL 104, 67005 (2013)] of a composition-induced change from c-axis ordered-moment alignment in a collinear A-type AFM structure (AFMI) at small x to abplane alignment in an unknown AFM structure (AFMII) at larger x in Ca1−xSrxCo2−yAs2 with the body-centered tetragonal ThCr2Si2 structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2 x 0.3 between these two phases. In this region the magnetic susceptibility versus temperature χ ab (T ) measured with magnetic fields H applied in the ab plane exhibit typical AFM behaviors with cusps at the Néel temperatures of ∼ 65 K, whereas χc(T ) and the low-temperature isothermal magnetization Mc(H) with H aligned along the c axis exhibit extremely soft ferromagnetic-like behaviors.Much research since 2008 has focused on studies of iron-based layered pnictides and chalcogenides due to their unique lattice, electronic, magnetic and superconducting properties [1][2][3][4][5][6]. An important family of these materials is comprised of doped and undoped bodycentered tetragonal parent compounds AFe 2 As 2 (A = Ca, Sr, Ba, Eu) with the ThCr 2 Si 2 -type structure (122-type compounds). The undoped and underdoped AFe 2 As 2 compounds exhibit a tetragonal to orthorhombic distortion of the crystal structure at T S 200 K. They also exhibit itinerant collinear antiferromagnetic (AFM) spindensity-wave ordering at a temperature T N the same or slightly lower than T S . The ordered moments in the stripe AFM structure of the orthorhombic phase are oriented in the ab plane. In 2014 a temperature Tinduced AFM spin-reorientation transition to a new AFM C 4 phase was discovered in the hole-underdoped Ba 1−x Na x Fe 2 As 2 system upon cooling below T N that can coexist with superconductivity [7]. A subsequent investigation by polarized and unpolarized neutron diffraction determined that the ordered moments in the new phase are aligned along the c axis instead of along the ab plane as in the stripe AFM structure [8]. The work on the Ba 1−x Na x Fe 2 As 2 system was followed by the observation of the same AFM C 4 phase in the Ba 1−x K x Fe 2 As 2 [9-11], Sr 1−x Na x Fe 2 As 2 [12, 13], and Ca 1−x Na x Fe 2 As 2 [14] systems. These results are important to understanding the mechanism of superconductivity and other aspects of the hole-doped iron arsenides [15][16][17][18][19][20][21].A similar but composition-induced moment realignment was suggested to occur in the isostructural CoAsbased system Ca 1−x Sr x Co 2−y As 2 [22]. CaCo 2−y As 2 has a so-called collapsed-tetragonal (cT) structure with AsAs bonding along the c axis between adjacent CoAs layers [23] and has ≈ 7% vacancies on the Co sites [24,25]. It exhibits itinerant A-type AFM ordering below T N = 52-77 K, depending on the sample, with the ordered moments of ≈ 0.3-0.4 µ B /Co (µ B is the Bohr magneton) within an ab-plane Co layer aligned ferromagnetically (FM) along the c axis and with AFM alignments between moments in adjacent Co planes [24][25][26][27][28]. The domi...

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supporting

confidence: 57%

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2
Sangeetha¹,
Smetana²,
Mudring³
et al. 2017
Phys. Rev. Lett.
21
3
54
0
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“…Samples with Co vacancies seem to have lower values for T N , with T N = 52(1) K for y = 0.14 [17] and T N = 76 K for y = 0 [28]. On the other hand, it has been suggested that vacancies alone may not explain the differing values of T N from different reports and that different growth conditions may also be responsible [30].…”

Section: Resultsmentioning

confidence: 95%

Antiferromagnetic stacking of ferromagnetic layers and doping-controlled phase competition in Ca1−xSrxCo2−yAs2
Li
¹
,
Sizyuk
²
,
Sangeetha
³

et al. 2019
Phys. Rev. B
16
3
22
0
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In search of a quantum phase transition between the two-dimensional (2D) ferromagnetism of CaCo2−yAs2 and stripe-type antiferromagnetism in SrCo2 As2, we instead find evidence for 1D magnetic frustration between magnetic square Co layers. We present neutron-diffraction data for Ca1−x Srx Co2−y As2 that reveal a sequence of x -dependent magnetic transitions which involve different stacking of 2 D ferromagnetically aligned layers with different magnetic anisotropy. We explain the x-dependent changes to the magnetic order by utilizing classical analytical calculations of a 1D Heisenberg model where single-ion magnetic anisotropy and frustration of antiferromagnetic nearest-and next-nearest-layer exchange interactions are all composition dependent.In search of a quantum phase transition between the two-dimensional (2D) ferromagnetism of CaCo 2−y As 2 and stripe-type antiferromagnetism in SrCo 2 As 2 , we instead find evidence for 1D magnetic frustration between magnetic square Co layers. We present neutron-diffraction data for Ca 1−x Sr x Co 2−y As 2 that reveal a sequence of x-dependent magnetic transitions which involve different stacking of 2D ferromagnetically aligned layers with different magnetic anisotropy. We explain the x-dependent changes to the magnetic order by utilizing classical analytical calculations of a 1D Heisenberg model where single-ion magnetic anisotropy and frustration of antiferromagnetic nearest-and next-nearest-layer exchange interactions are all composition dependent.

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“…What differentiates the B-T phase diagram of (NH 4 ) 2 FeCl 5 ⋅H 2 O from that of other molecule-based multiferroics is the exceptional level of detail. For instance, in metal-organic framework compounds such as (CH 3 ) 2 NH 2 ]Mn(HCOO) 3 , the phase diagram exhibits a spin flop near 0.3 T, a broad canted phase, and a transition to the fully saturated state at 15.3 T. 22 Likewise, in CaCo 2 As 2 , the critical fields are 3.7 and 7.5 T. 46 The overall simplicity of these B-T phase diagrams arises from the superexchange pathways through formate ligands or Co⋯As interactions, respectively. Magnetic exchange, of course, can also take place through hydrogen and halide bonds.…”

Section: Resultsmentioning

confidence: 99%

Magnetic field-temperature phase diagram of multiferroic (NH4)2FeCl5·H2O

et al. 2019

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Owing to their overall low energy scales, flexible molecular architectures, and ease of chemical substitution, molecule-based multiferroics are extraordinarily responsive to external stimuli and exhibit remarkably rich phase diagrams. Even so, the stability and microscopic properties of various magnetic states in close proximity to quantum critical points are highly under-explored in these materials. Inspired by these opportunities, we combined pulsed-field magnetization, first-principles calculations, and numerical simulations to reveal the magnetic field-temperature (B-T) phase diagram of multiferroic (NH 4 ) 2 FeCl 5 ⋅H 2 O. In this system, a network of intermolecular hydrogen and halogen bonds creates a competing set of exchange interactions that generates additional structure in the phase diagram-both in the vicinity of the spin flop and near the 30 T transition to the fully saturated state. Consequently, the phase diagrams of (NH 4 ) 2 FeCl 5 ⋅H 2 O and its deuterated analog are much more complex than those of other molecule-based multiferroics. The entire series of coupled electric and magnetic transitions can be accessed with a powered magnet, opening the door to exploration and control of properties in this and related materials.npj Quantum Materials (2019) 4:44 ; https://doi.

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Spin-flop transition and magnetic phase diagram inCaCo2As2revealed by torque measurements

Cited by 29 publications

References 40 publications

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2
Sangeetha¹,
Smetana²,
Mudring³
et al. 2017
Phys. Rev. Lett.
21
3
54
0
View full text Add to dashboard Cite

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2
Sangeetha¹,
Smetana²,
Mudring³
et al. 2017
Phys. Rev. Lett.
21
3
54
0
View full text Add to dashboard Cite

Antiferromagnetic stacking of ferromagnetic layers and doping-controlled phase competition in Ca1−xSrxCo2−yAs2
Li
¹
,
Sizyuk
²
,
Sangeetha
³

et al. 2019
Phys. Rev. B
16
3
22
0
View full text Add to dashboard Cite

Magnetic field-temperature phase diagram of multiferroic (NH4)2FeCl5·H2O

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Spin-flop transition and magnetic phase diagram inCaCo2As2revealed by torque measurements

Cited by 29 publications

References 40 publications

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2Sangeetha1, Smetana2, Mudring3 et al. 2017Phys. Rev. Lett.213540View full textAdd to dashboardCite

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2Sangeetha1, Smetana2, Mudring3 et al. 2017Phys. Rev. Lett.213540View full textAdd to dashboardCite

Antiferromagnetic stacking of ferromagnetic layers and doping-controlled phase competition in Ca1−xSrxCo2−yAs2Li1, Sizyuk2, Sangeetha3 et al. 2019Phys. Rev. B163220View full textAdd to dashboardCite

Magnetic field-temperature phase diagram of multiferroic (NH4)2FeCl5·H2O

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Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2
Sangeetha¹,
Smetana²,
Mudring³
et al. 2017
Phys. Rev. Lett.
21
3
54
0
View full text Add to dashboard Cite

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron AntiferromagnetCa1−xSrxCo2−yAs2
Sangeetha¹,
Smetana²,
Mudring³
et al. 2017
Phys. Rev. Lett.
21
3
54
0
View full text Add to dashboard Cite

Antiferromagnetic stacking of ferromagnetic layers and doping-controlled phase competition in Ca1−xSrxCo2−yAs2
Li
¹
,
Sizyuk
²
,
Sangeetha
³

et al. 2019
Phys. Rev. B
16
3
22
0
View full text Add to dashboard Cite