Magnetic order and fluctuations in the presence of quenched disorder in the kagome staircase system (Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Mg<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mi>x</mml:mi></mml:msub></mml:math>)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>3</mml:mn></mml:msub></mml:math>V<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>8</mml:mn></mml:msub></mml:math>
Bibliographic record
Abstract
Co${}_{3}$V${}_{2}$O${}_{8}$ is an orthorhombic magnet in which $S=3/2$ magnetic moments reside on two crystallographically inequivalent Co${}^{2+}$ sites, which decorate a stacked, buckled version of the two-dimensional kagome lattice, the stacked kagome staircase. The magnetic interactions between the Co${}^{2+}$ moments in this structure lead to a complex magnetic phase diagram at low temperature, wherein it exhibits a series of five transitions below 11 K that ultimately culminate in a ferromagnetic ground state below $T\ensuremath{\sim}6.2$ K. Here we report magnetization measurements on single- and polycrystalline samples of (Co${}_{1\ensuremath{-}x}$Mg${}_{x}$)${}_{3}$V${}_{2}$O${}_{8}$ for $x<0.23$, as well as elastic and inelastic neutron scattering measurements on single crystals of magnetically dilute (Co${}_{1\ensuremath{-}x}$Mg${}_{x}$)${}_{3}$V${}_{2}$O${}_{8}$ for $x=0.029$ and $x=0.194$, in which nonmagnetic Mg${}^{2+}$ ions substitute for magnetic Co${}^{2+}$. We find that a dilution of 2.9$%$ leads to a suppression of the ferromagnetic transition temperature by $\ensuremath{\sim}$15$%$ while a dilution level of 19.4$%$ is sufficient to destroy ferromagnetic long-range order in this material down to a temperature of at least 1.5 K. The magnetic excitation spectrum is characterized by two spin wave branches in the ordered phase for (Co${}_{1\ensuremath{-}x}$Mg${}_{x}$)${}_{3}$V${}_{2}$O${}_{8}$ ($x=0.029$), similar to that of the pure $x=0$ material, and by broad diffuse scattering at temperatures below 10 K in (Co${}_{1\ensuremath{-}x}$Mg${}_{x}$)${}_{3}$V${}_{2}$O${}_{8}$ ($x=0.194$). Such a strong dependence of the transition temperatures on long-range order in the presence of quenched nonmagnetic impurities is consistent with two-dimensional physics driving the transitions. We further provide a simple percolation model that semiquantitatively explains the inability of this system to establish long-range magnetic order at the unusually low dilution levels which we observe in our experiments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".