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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.010 | 0.007 |
| Meta-epidemiology (narrow) | 0.006 | 0.010 |
| Meta-epidemiology (broad) | 0.003 | 0.010 |
| Bibliometrics | 0.002 | 0.007 |
| Science and technology studies | 0.008 | 0.009 |
| Scholarly communication | 0.007 | 0.009 |
| Open science | 0.012 | 0.010 |
| Research integrity | 0.009 | 0.011 |
| Insufficient payload (model declined to judge) | 0.047 | 0.011 |
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; both teacher heads agree on what is shown here.
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".